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2.
JSES Int ; 7(6): 2420-2424, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37969510

RESUMO

Background: End-stage renal disease (ESRD) and renal transplant (RT) patients are known to have more perioperative and postoperative complications after arthroplasty surgeries when compared to patients without. We hypothesize that RT patients undergoing shoulder arthroplasty (SA) have fewer systemic and surgical complications when compared to ESRD patients undergoing SA. Methods: This was a retrospective review from the PearlDiver Patient Record Database. International Classification of Diseases and Current Procedural Terminology codes were used to identify patients who had undergone primary total and reverse shoulder arthroplasty, respectively, and subsequent surgical revisions. Unadjusted univariate analysis of patient demographics, Charlson Cormorbidty Index, and surgical complications at 90 days, 1 year, and 2 years after was performed using chi-squared testing. Multivariate logistic regression analyses were subsequently performed for systemic complications and prosthesis outcomes at all time points. Results: Of 1191 patients with ESRD or previous RT and who underwent either total shoulder arthroplasty or reverse total shoulder arthroplasty, 1042 (87.5%) had ESRD and 149 (12.5%) had a previous RT. ESRD SA patients were more likely to have hypertension, liver disease, coronary artery disease, and hypothyroidism. Interestingly no statistical significance was found in multivariate analysis for systemic complications at 90 days, nor for surgical complications at the 90-day, 1-year, or 2-year mark between ESRD and RT cohorts. Conclusion: SAs have comparable outcomes in ESRD and RT patients. The differing conclusions among studies might be partially accounted for by the demographic differences and comorbidities between these 2 patient populations. Providers should continue to provide appropriate counseling concerning risks, benefits, and timing of SA for these patients.

3.
OTA Int ; 6(4): e289, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37901451

RESUMO

Objective: We aimed to evaluate the difference in 30-day outcomes after surgical management of proximal humerus fractures (PHFs) between patients with and without chronic liver disease as defined by a MELD score greater than 10. Design: This was a retrospective database review. Setting: All centers participating in the American College of Surgeons National Surgical Quality Improvement Program database were included. Patients/Participants: Patients with proximal humerus fractures who (1) underwent ORIF, HA, or SA and (2) had calculable MELD scores were included. Intervention: Open reduction and internal fixation, hemiarthroplasty, or shoulder arthroplasty was used for treatment. Main outcome measurements: Thirty-day complications, mortality, readmission, and reoperation rates were measured. Results: Of the total 1732 PHF patients identified, 300 had a MELD score higher than 10. After propensity matching by significant covariates, MELD score higher than 10 was found to be significantly associated with higher rates of 30-day mortality, 30-day readmission, transfusion within 72 hours, and systemic complications. Among patients with a MELD score higher than 10, treatment with SA or HA instead of ORIF was associated with a higher rate of transfusion and longer operative time. There were no significant differences between treatment cohorts regarding mortality, reoperation, readmission, or complications. Conclusions: A MELD score higher than 10 is associated with higher risk of surgical complications, transfusion, and death in patients undergoing surgery for proximal humerus fractures. Among patients with a MELD score higher than 10, ORIF was associated with a lower transfusion rate and shorter operative time than arthroplasty or hemiarthroplasty. Level of Evidence: Prognostic Level III.

4.
J Shoulder Elb Arthroplast ; 7: 24715492231192068, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37559885

RESUMO

Introduction: The most common surgical options for geriatric proximal humerus fractures are open reduction and internal fixation (ORIF), hemiarthroplasty (HA), and reverse total shoulder arthroplasty. We used a longitudinal inpatient discharge database to determine the cumulative incidence of conversion to arthroplasty after ORIF of geriatric proximal humerus fractures. The rates of short-term complications and all-cause reoperation were also compared. Patients and Methods: All patients 65 or older who sustained a proximal humerus fracture and underwent either ORIF, HA, or shoulder arthroplasty (SA) as an inpatient from 2000 through 2017 were identified. Survival analysis was performed with ORIF conversion to arthroplasty and all-cause reoperation as the endpoints of interest. Rates of 30-day readmission and short-term complications were compared. Trends in procedure choice and outcomes over the study period were analyzed. Results: A total of 27 102 geriatric patients that underwent inpatient surgical management of proximal humerus fractures were identified. Among geriatric patients undergoing ORIF, the cumulative incidence of conversion to arthroplasty within 10 years was 8.2%. The 10-year cumulative incidence of all-cause reoperation was 12.1% for ORIF patients and less than 4% for both HA and SA patients. Female sex was associated with increased risk of ORIF conversion and younger age was associated with higher all-cause reoperation. ORIF was associated with higher 30-day readmission and short-term complication rates. Over the study period, the proportion of patients treated with ORIF or SA increased while the proportion of patients treated with HA decreased. Short-term complication rates were similar between arthroplasty and ORIF patients in the later cohort (2015-2017). Conclusion: The 10-year cumulative incidence of conversion to arthroplasty for geriatric patients undergoing proximal humerus ORIF as an inpatient was found to be 8.2%. All-cause reoperations, short-term complications, and 30-day readmissions were all significantly lower among patients undergoing arthroplasty, but the difference in complication rate between arthroplasty and ORIF was attenuated in more recent years. Younger age was a risk factor for reoperation and female sex was associated with increased risk of requiring conversion to arthroplasty after ORIF.

5.
J Arthroplasty ; 38(11): 2336-2341.e1, 2023 11.
Artigo em Inglês | MEDLINE | ID: mdl-37236290

RESUMO

BACKGROUND: Total knee arthroplasty (TKA) in end-stage renal disease is associated with complications. Controversy exists whether elective TKA should be performed while patients are on hemodialysis (HD) or following renal transplant (RT). This study compares TKA outcomes in HD versus RT patients. METHODS: A national database was retrospectively reviewed using International Classification of Diseases codes to identify HD and RT patients who underwent primary TKA from 2010 to 2018. Demographics, comorbidities, and hospital factors were compared using Wald and Chi-squared tests. The primary outcome was in-hospital mortalities while secondary outcomes included quality outcomes and medical/surgical complications. Multivariate regressions were used to determine independent associations. Significance was determined with a 2-tailed P value of .05. There were 13,611 patients who underwent TKA (61.1 HD and 38.9% RT). Patients who had RT were younger, had fewer comorbidities, and more likely to have private insurance. RESULTS: The RT patients had a lower rate of mortality (odds ratio (OR) 0.23, P < .01)), complications (OR 0.63, P < .01), cardiopulmonary complications (OR 0.44, P = .02), sepsis (OR 0.22, P < .001), and blood transfusion (OR 0.35, P < .001) during the index hospitalization. This cohort was also found to have decreased length of stay (-2.0 days, P < .001), non-home discharge (OR 0.57, P < .001), and hospital cost (-$5,300, P < .001). Patients who had RT had a lower rate of readmission (OR 0.54, P < .001), periprosthetic joint infection (OR 0.50, P < .01), and surgical site infection (OR 0.37, P < .001) within 90 days. CONCLUSION: These findings suggest that HD patients are a high-risk population in TKA compared to RT patients and warrant stringent perioperative monitoring.


Assuntos
Artroplastia de Quadril , Artroplastia do Joelho , Transplante de Rim , Humanos , Artroplastia do Joelho/efeitos adversos , Estudos Retrospectivos , Transplante de Rim/efeitos adversos , Fatores de Risco , Diálise Renal/efeitos adversos , Tempo de Internação , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/etiologia , Readmissão do Paciente , Artroplastia de Quadril/efeitos adversos
6.
Hip Int ; 33(4): 640-648, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35437061

RESUMO

INTRODUCTION: Total hip arthroplasty (THA) in end-stage renal disease (ESRD) patients is associated with increased complications. Controversy exists whether elective THA should be performed while these patients are on haemodialysis (HD) or following renal transplant (RT). This study seeks to compare THA outcomes in HD versus RT patients. METHODS: A national database was retrospectively reviewed using ICD codes to identify all HD and RT patients who underwent primary THA from 2010 to 2018. Demographics, comorbidities, and hospital factors were compared between cohorts using Wald and chi-square tests. The primary outcome was in-hospital mortality, while secondary outcomes included length of stay (LOS), non-home discharge, cost, readmission, and medical/surgical complications. Multivariate regression was used to determine independent associations. Significance was determined with a 2-tailed p-value of 0.05. RESULTS: 11,133 patients underwent THA, 61.6% HD and 39.4% RT patients. RT patients were younger, had fewer comorbidities, and more likely to have private insurance. After adjusting for these differences, RT patients had a lower rate of mortality (OR 0.31, p = 0.01), complications (OR 0.54, p < 0.01), cardiopulmonary complications (OR 0.54, p = 0.04), sepsis (OR 0.43, p < 0.01), and blood transfusion (OR 0.39, p < 0.001) during the index hospitalisation. RT was associated with decreased LOS (-2.0 days, p < 0.001), non-home discharge (OR 0.35, p < 0.001), and hospital cost (-$6,000, p < 0.001). RT had a lower rate of readmission (OR 0.60, p < 0.001) and revision surgery (OR 0.24, p = 0.01) within 90 days. CONCLUSIONS: These findings suggest HD patients are a high-risk population in THA compared to RT patients and warrant stringent perioperative monitoring.


Assuntos
Artroplastia de Quadril , Transplante de Rim , Humanos , Artroplastia de Quadril/efeitos adversos , Transplante de Rim/efeitos adversos , Estudos Retrospectivos , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/etiologia , Readmissão do Paciente , Fatores de Risco , Tempo de Internação
7.
JSES Int ; 6(5): 736-742, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-36081687

RESUMO

Background: Renal osteodystrophy predisposes renal disease patients to fracture. Proximal humerus fractures (PHFs) frequently undergo open reduction internal fixation (ORIF); however, the effect of renal disease on outcomes is unknown. Methods: A retrospective review of the Nationwide Readmissions Database used International Classification of Diseases, 9th Revision, codes to identify patients who underwent ORIF for closed PHF from 2010 to 2014 with no renal disease, predialysis chronic renal disease (CRD), and end-stage renal disease (ESRD). Results: A total of 85,433 patients were identified, including 5498 (6.4%) CRD and 636 (0.7%) ESRD. CRD and ESRD patients had increased age, comorbidities, and rates of Medicare insurance. After adjusting for differences, CRD and ESRD patients were at increased risk of any complication (odds ratio [OR] 2.48, 1.66), blood transfusion (OR 1.85, 3.31), respiratory complications (OR 1.14, 1.59), acute renal failure (OR 4.80, 1.67), systemic infection (OR 2.00, 3.14), surgical site infection (OR 1.52, 3.87), longer length of stay (7.1 and 12.9 days vs. 5.9 days), and higher cost ($21,669 and $35,413 vs. $20,394) during index hospitalization, as well as surgical site infection (OR 1.43, 3.03) and readmission (OR 1.61, 3.69) within 90 days of discharge, respectively, compared with no renal disease patients. During index hospitalization, CRD patients also had increased risk for periprosthetic fracture (OR 4.97) and cardiac complications (OR 1.47), whereas ESRD patients had increased risk of mortality (OR 5.79), wound complication (2.67), and deep vein thrombosis (OR 16.70). Conclusion: These findings suggest renal patients are at increased risk for complications after PHF ORIF, highlighting the importance of close perioperative monitoring and appropriate patient selection in this population, including strong consideration of nonoperative management.

8.
Arthroplast Today ; 15: 188-195.e6, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35774881

RESUMO

Background: As primary total knee arthroplasty volume continues to increase, so will the number of revision total knee arthroplasty (rTKA) procedures. The purpose of this study is to provide an updated perspective on the incidence, indications, and financial burden of rTKA in the United States. Material and methods: This was a retrospective epidemiologic analysis using the National Inpatient Sample. International Classification of Diseases ninth and tenth revision codes were used to identify patients who underwent rTKA and create cohorts based on rTKA indications from 2012 to 2019. National and regional trends for length of stay, cost, and discharge location were evaluated. Results: A total of 505,160 rTKA procedures were identified. The annual number of rTKA procedures increased by 29.6% over the study period (56,490 to 73,205). The top 3 indications for rTKA were aseptic loosening (23.1%), periprosthetic joint infection (PJI) (20.4%), and instability (11.0%). Over the study period, the proportion of patients discharged to skilled nursing facility decreased from 31.7% to 24.1% (P < .001). Hospital length of stay decreased from 4.0 days in 2012 to 3.8 days in 2019 (P < .001). Hospital costs increased by $1300 from $25,730 to $27,077 (P < .001). The proportion of rTKA cases performed at urban academic centers increased (52.1% to 74.3%, P < .001) while that at urban nonacademic centers decreased (39.0% to 19.2%, P < .001). Conclusion: The top 3 indications for rTKA were aseptic loosening, PJI, and instability, with PJI becoming the most common indication in 2019. These cases are increasingly being performed at urban academic centers and away from urban nonacademic centers. Level of Evidence: 3 (Retrospective cohort study).

9.
JBJS Case Connect ; 12(4)2022 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-36705258

RESUMO

UPDATE: This article was updated on January 27, 2023, because of a previous error. One of the author's degrees was incorrect. Anirudh Eranki's degree was listed as BS, but this author did not have a degree at time of publication.An erratum (JBJS Case Connect. 2023;13[1]:e22.00522ER) has been published for this article.


Assuntos
Tendão do Calcâneo , Lacerações , Traumatismos dos Tendões , Humanos , Traumatismos dos Tendões/cirurgia , Ruptura/cirurgia , Transplante Homólogo , Tendão do Calcâneo/cirurgia , Tendão do Calcâneo/lesões , Aloenxertos
10.
Neurospine ; 17(2): 407-416, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32615699

RESUMO

OBJECTIVE: Current guidelines recommend initiation of venous thromboembolism (VTE) chemoprophylaxis within 72 hours of spinal cord injury (SCI). This study investigated the safety and efficacy of chemoprophylaxis within 24 hours of surgery for SCI. METHODS: A retrospective review of 97 consecutive patients who underwent surgery for acute traumatic SCI at a single level 1 trauma center from 2013-2018 was performed. VTE/postoperative bleeding rates during hospitalization, demographics, medical/surgical complications, drain output, length of stay, and disposition were obtained. Chi-square with odds ratios (ORs), 1-way analysis of variance, and logistic regression were performed to establish significant differences between groups. RESULTS: Seventy-nine patients were included, 49 received chemoprophylaxis within 24 hours and 20 within 24-72 hours. Cohort characteristics included an average age of 51.8 years, 77.2% male, 62.0% cervical, and 35.4% thoracic SCIs. Using the American Spinal Injury Association Impairment Scale (AIS), 39.2% were AIS-A injuries, 19.0% AIS-B, 25.3% AIS-C, and 16.5% AIS-D. Unfractionated heparin was administered in 88.6% of patients and 11.4% received low molecular weight heparin. Chemoprophylaxis within 24 hours of surgery was associated with a lower rate of VTE (6.1% vs. 35.0%; OR, 0.121; 95% confidence interval [CI], 0.027-0.535) and deep vein thrombosis (4.1% vs. 30.0%; OR, 0.099; 95% CI, 0.018-0.548) versus 24-72 hours. Pulmonary embolism rates were not significantly different (6.1% vs. 5.0%, p = 1.0). There were no postoperative bleeding complications and no significant difference in drain output between cohorts. CONCLUSION: Early VTE chemoprophylaxis is effective with lower VTE rates when initiated within 24 hours of surgery for SCI and is safe with no observed postoperative bleeding complications.

11.
Orthop J Sports Med ; 8(3): 2325967120906825, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32201707

RESUMO

BACKGROUND: There are 60 million US youth who participate in organized athletics, with large increases in both sport participation and specialization during the past 2 decades. There is some evidence that increased sport specialization and training volumes may be associated with increased injuries in adolescent populations. This study examines these variables in a population of elite college athletes. HYPOTHESIS: Early sport specialization (ESS) and a high training volume are risk factors for injury and/or surgery in National Collegiate Athletic Association (NCAA) Division I athletes. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: All Division I athletes at a single institution were surveyed regarding demographics, scholarship status, reason for specialization, age at specialization, training volume, and injury history. Chi-square and Mann-Whitney U tests were performed to identify significant differences. RESULTS: Athletes who specialized in their eventual varsity sport before age 14 years were more likely to report a history of injuries (86.9% vs 71.4%), multiple injuries (64.6% vs 48.8%), multiple college injuries (17.2% vs 6.0%), a greater number of total injuries (2.0 vs 1.0), and require more time out for an injury (15.2 vs 6.5 weeks) than those who did not. They were also more likely to be recruited (92.9% vs 82.1%) and receive a scholarship (82.8% vs 67.9%). Athletes who trained for greater than 28 hours per week in their eventual varsity sport before high school were more likely to report multiple injuries (90.0% vs 56.3%), multiple college injuries (40.0% vs 12.5%), a surgical injury (60.0% vs 22.9%), multiple surgical injuries (30.0% vs 4.7%), a greater number of total injuries (2.5 vs 2.0), and more time out for an injury (36.5 vs 11.0 weeks) than those who did not (all P < .05). However, these athletes were not more likely to be recruited (90.0% vs 89.8%) or receive a scholarship (80.0% vs 74.5%). CONCLUSION: NCAA Division I athletes with ESS and/or a high training volume sustained more injuries and missed more time because of an injury, but those with ESS were more likely to be recruited and receive a college scholarship. This knowledge can help inform discussions and decision making among athletes, parents, coaches, trainers, and physicians.

12.
J Spine Surg ; 6(4): 659-669, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33447668

RESUMO

BACKGROUND: Anterior lumbar interbody fusion (ALIF) is commonly utilized in lumbar degenerative pathologies. Standalone ALIF (ST-ALIF) systems were developed to avoid added morbidity, surgical time, and cost of anterior and posterior fusion (APF). Controversy exists in the literature about which of these two techniques yields superior clinical and radiographic outcomes, and few studies have directly compared them. This study seeks to compare ST-ALIF and APF in terms of sagittal correction and surgical complications. METHODS: Ninty-two consecutive ALIF cases performed from 2013-2018 were retrospectively reviewed and separated into 2 groups. Radiographic measurements were performed on pre- and post-operative radiographs, including segmental lordosis (SL), lumbar lordosis (LL), and pelvic incidence-lumbar lordosis mismatch (PI-LL). Surgical complications were determined. Statistical analysis was performed using chi-square test of homogeneity, Fisher's exact test, and independent sample t-test. Comparisons between groups were deemed statistically significant at the P<0.05 threshold. RESULTS: Fifty-seven ST-ALIF, 35 APF were identified. There were no differences in age, gender, BMI, Charlson Comorbidity Index (CCI), preoperative diagnosis, or surgical level between the 2 cohorts. Bone Morphogenetic Protein (BMP) was utilized in 24.6% of ST-ALIF versus none of APF (P=0.001). No differences were detected in SL, LL, and PI-LL mismatch. ST-ALIF cohort had significantly greater risk of subsidence and revision surgery versus APF (12.3% vs. 0%, RD 95% CI: 3.8-20.8%, P=0.042). Recurrent spondylolisthesis occurred in 5 ST-ALIF cases, 3 cases with implant failure, and 2 nonunions versus none in the APF group. CONCLUSIONS: ST-ALIF was associated with significantly greater subsidence and revision surgery versus APF. Careful patient selection is paramount when considering ST-ALIF. The potential for revision surgery may offset the potential benefit in avoiding posterior fusion. Despite the greater risk of subsidence, sagittal alignment was not significantly affected.

13.
Spine J ; 18(11): 1999-2008, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-29631061

RESUMO

BACKGROUND CONTEXT: Lumbar fusion is a popular and effective surgical option to provide stability and restore anatomy. Particular attention has recently been focused on sagittal alignment and radiographic spinopelvic parameters that apply to lumbar fusion as well as spinal deformity cases. Current literature has demonstrated the effectiveness of various techniques of lumbar fusion; however, comparative data of these techniques are limited. PURPOSE: This study aimed to directly compare the impact of various lumbar fusion techniques (anterior lumbar interbody fusion [ALIF], lateral lumbar interbody fusion [LLIF], transforaminal lumbar interbody fusion [TLIF], and posterolateral fusion [PLF]) based on radiographic parameters. STUDY DESIGN/SETTING: A single-center retrospective study examining preoperative and postoperative radiographs was carried out. PATIENT SAMPLE: A consecutive list of lumbar fusion surgeries performed by multiple spine surgeons at a single institution from 2013 to 2016 was identified. OUTCOME MEASURES: Radiographic measurements used included segmental lordosis (SL), lumbar lordosis (LL), pelvic incidence (PI), pelvic incidence-lumbar lordosis (PI-LL) mismatch, anterior and posterior disc height (DH-A, DH-P, respectively), and foraminal height (FH). METHODS: Radiographic measurements were performed on preoperative and postoperative lateral lumbar radiographs on all single-level lumbar fusion cases. Demographic data were collected including age, gender, approach, diagnosis, surgical level, and implant lordosis. Paired sample t test, one-way analysis of variance (ANOVA), McNemar test, and independent sample t test were used to establish significant differences in the outcome measures. Multiple linear regression was performed to determine a predictive model for lordosis from implant lordosis, fusion technique, and surgical level. RESULTS: There were 164 patients (78 men, 86 women) with a mean age of 60.1 years and average radiographic follow-up time of 9.3 months. These included 34 ALIF, 23 LLIF, 63 TLIF, and 44 PLF surgeries. ALIF and LLIF significantly improved SL (7.9° and 4.4°), LL (5.5° and 7.7°), DH-A (8.8 mm and 5.8 mm), DH-P (3.4 mm and 2.3 mm), and FH (2.8 mm and 2.5 mm), respectively (p≤.003). TLIF significantly improved these parameters, albeit to a lesser extent: SL (1.7°), LL (2.7°), DH-A (1.1 mm), DH-P (0.8 mm), and FH (1.1 mm) (p≤.02). PLF did not significantly alter any of these parameters while significantly reducing FH (-1.3 mm, p=.01). One-way ANOVA showed no significant differences between ALIF and LLIF other than ALIF with greater ΔDH-A (3.0 mm, p=.02). Both ALIF and LLIF significantly outperformed PLF in preoperative to postoperative changes in all parameters p≤.001. Additionally, ALIF significantly outperformed TLIF in the change in SL (6.2°, p<.001), and LLIF significantly outperformed TLIF in the change in LL (5.0°, p=.02). Both outperformed TLIF in ΔDH-A (7.7 mm and 4.7 mm) and ΔDH-P (2.6 mm and 1.5 mm), respectively (p≤.02). ALIF was the only fusion technique that significantly improved the proportion of patients with a PI-LL<10° (0.410.66, p=.02). Lordotic cages had superior improvement of all parameters compared with non-lordotic cages (p<.001). Implant lordosis (m=1.1), fusion technique (m=6.8), and surgical level (m=6.9) significantly predicted postoperative SL (p<.001, R2=0.56). CONCLUSIONS: This study demonstrated that these four lumbar fusion techniques yield divergent radiographic results. ALIF and LLIF produced greater improvements in radiographic measurements postoperatively compared with TLIF and PLF. ALIF was the most successful in improving PI-LL mismatch, an important parameter relating to sagittal alignment. Lordotic implants provided better sagittal correction and surgeons should be cognizant of the impact that these differing implants and techniques produce after surgery. Surgical technique is an important determinant of postoperative alignment and has ramifications upon sagittal alignment in lumbar fusion surgery.


Assuntos
Vértebras Lombares/cirurgia , Complicações Pós-Operatórias/epidemiologia , Fusão Vertebral/métodos , Adulto , Idoso , Feminino , Humanos , Vértebras Lombares/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Complicações Pós-Operatórias/diagnóstico por imagem , Complicações Pós-Operatórias/etiologia , Radiografia , Fusão Vertebral/efeitos adversos
14.
J Am Chem Soc ; 139(31): 10702-10714, 2017 08 09.
Artigo em Inglês | MEDLINE | ID: mdl-28749693

RESUMO

A conformationally flexible template for the meta-C-H olefination of benzoic acids was designed through both experimental and computational efforts. The newly designed template favors a silver-palladium heterodimer low barrier transition state, and demonstrates that it is feasible to lengthen templates so as to achieve meta-selectivity when the distance between the functional handle of the native substrate and target C-H bond decreases. Analysis of the ortho-, meta-, and para-C-H cleavage transition states determined that the new template conformation optimizes the interaction between the nitrile and palladium-silver dimer in the meta-transition state, enabling palladium to cleave meta-C-H bonds with moderate-to-good yields and generally high regioselectivity. Regioselectivity is governed exclusively by the template, and kinetic experiments reveal that there is a 4-fold increase in rate in the presence of monoprotected amino acid ligands. Using a Boltzmann distribution of all accessible C-H activation transition states, it is possible to computationally predict meta-selectivity in a number of investigated templates with reasonable accuracy. Structural and distortion energies reported may be used for the further development of templates for meta-C-H activation of hitherto unexplored arene substrates.


Assuntos
Benzoatos/química , Metais/química , Conformação Molecular , Nitrilas/química , Paládio/química , Prata/química
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