Inverse Isotope Effects in Single-Crystal to Single-Crystal Reactivity and the Isolation of a Rhodium Cyclooctane σ-Alkane Complex.

The sequential solid/gas single-crystal to single-crystal reaction of [Rh(Cy2P(CH2)3PCy2)(COD)][BArF 4] (COD = cyclooctadiene) with H2 or D2 was followed in situ by solid-state 31P{1H} NMR spectroscopy (SSNMR) and ex situ by solution quenching and GC-MS. This was quantified using a two-step Johnson-Mehl-Avrami-Kologoromov (JMAK) model that revealed an inverse isotope effect for the second addition of H2, that forms a σ-alkane complex [Rh(Cy2P(CH2)3PCy2)(COA)][BArF 4]. Using D2, a temporal window is determined in which a structural solution for this σ-alkane complex is possible, which reveals an η2,η2-binding mode to the Rh(I) center, as supported by periodic density functional theory (DFT) calculations. Extensive H/D exchange occurs during the addition of D2, as promoted by the solid-state microenvironment.

MicroED characterization of a robust cationic σ-alkane complex stabilized by the [B(3,5-(SF5)2C6H3)4]- anion, via on-grid solid/gas single-crystal to single-crystal reactivity.

Microcrystalline (∼1 µm) [Rh(Cy2PCH2CH2PCy2)(norbornadiene)][S-BArF4], [S-BArF4] = [B(3,5-(SF5)2C6H3)4]-, reacts with H2 in a single-crystal to single-crystal transformation to form the σ-alkane complex [Rh(Cy2PCH2CH2PCy2)(norbornane)][S-BArF4], for which the structure was determined by microcrystal Electron Diffraction (microED), to 0.95 Å resolution, via an on-grid hydrogenation, and a complementary single-crystal X-ray diffraction study on larger, but challenging to isolate, crystals. Comparison with the [BArF4]- analogue [ArF = 3,5-(CF3)2(C6H3)] shows that the [S-BArF4]- anion makes the σ-alkane complex robust towards decomposition both thermally and when suspended in pentane. Subsequent reactivity with dissolved ethene in a pentane slurry, forms [Rh(Cy2PCH2CH2PCy2)(ethene)2][S-BArF4], and the catalytic dimerisation/isomerisation of ethene to 2-butenes. The increased stability of [S-BArF4]- salts is identified as being due to increased non-covalent interactions in the lattice, resulting in a solid-state molecular organometallic material with desirable stability characteristics.

A phase II trial of selumetinib in children with recurrent optic pathway and hypothalamic low-grade glioma without NF1: a Pediatric Brain Tumor Consortium study.

BACKGROUND: Pediatric low-grade gliomas (pLGGs) are the most common childhood brain tumor. Progression-free survival (PFS) is much lower than overall survival, emphasizing the need for alternative treatments. Sporadic (without neurofibromatosis type 1) optic pathway and hypothalamic gliomas (OPHGs) are often multiply recurrent and cause significant visual deficits. Recently, there has been a prioritization of functional outcomes. METHODS: We present results from children with recurrent/progressive OPHGs treated on a PBTC (Pediatric Brain Tumor Consortium) phase II trial evaluating efficacy of selumetinib (AZD6244, ARRY-142886) a MEK-1/2 inhibitor. Stratum 4 of PBTC-029 included patients with sporadic recurrent/progressive OPHGs treated with selumetinib at the recommended phase II dose (25mg/m2/dose BID) for a maximum of 26 courses. RESULTS: Twenty-five eligible and evaluable patients were enrolled with a median of 4 (1-11) previous therapies. Six of 25 (24%) had partial response, 14/25 (56%) had stable disease, and 5 (20%) had progressive disease while on treatment. The median treatment courses were 26 (2-26); 14/25 patients completed all 26 courses. Two-year PFS was 78 ± 8.5%. Nineteen of 25 patients were evaluable for visual acuity which improved in 4/19 patients (21%), was stable in 13/19 (68%), and worsened in 2/19 (11%). Five of 19 patients (26%) had improved visual fields and 14/19 (74%) were stable. The most common toxicities were grade 1/2 CPK elevation, anemia, diarrhea, headache, nausea/emesis, fatigue, AST and ALT increase, hypoalbuminemia, and rash. CONCLUSIONS: Selumetinib was tolerable and led to responses and prolonged disease stability in children with recurrent/progressive OPHGs based upon radiographic response, PFS, and visual outcomes.

Selectivity of Rh⋠⋠⋠H-C Binding in a σ-Alkane Complex Controlled by the Secondary Microenvironment in the Solid State.

Single-crystal to single-crystal solid-state molecular organometallic (SMOM) techniques are used for the synthesis and structural characterization of the σ-alkane complex [Rh(tBu2 PCH2 CH2 CH2 PtBu2 )(η2 ,η2 -C7 H12 )][BArF 4 ] (ArF =3,5-(CF3 )2 C6 H3 ), in which the alkane (norbornane) binds through two exo-C-H⋅⋅⋅Rh interactions. In contrast, the bis-cyclohexyl phosphine analogue shows endo-alkane binding. A comparison of the two systems, supported by periodic DFT calculations, NCI plots and Hirshfeld surface analyses, traces this different regioselectivity to subtle changes in the local microenvironment surrounding the alkane ligand. A tertiary periodic structure supporting a secondary microenvironment that controls binding at the metal site has parallels with enzymes. The new σ-alkane complex is also a catalyst for solid/gas 1-butene isomerization, and catalyst resting states are identified for this.

The ditungsten decacarbonyl dianion.

We report the synthesis and structural authentication of the ditungsten decarbonyl dianion in [(OC)5W-W(CO)5][K(18-crown-6)(THF)2]2 (1), completing the group 6 dianion triad over half a century since the area began. The W-W bond is long [3.2419(8) Å] and, surprisingly, in the solid-state the dianion adopts a D4h eclipsed rather than D4d staggered geometry, the latter of which dominates the structural chemistry of binary homobimetallic carbonyls. Computational studies at levels of theory from DFT to CCSD(T) confirm that the D4d geometry is energetically preferred in the gas-phase, being ∼18 kJ mol-1 more stable than the D4h form, since slight destabilisation of the degenerate W-CO π 5dxz and 5dyz orbitals is outweighed by greater stabilisation of the W-W σ-bond orbital. The gas-phase D4h structure displays a single imaginary vibrational mode, intrinsic reaction coordinate analysis of which links the D4h isomer directly to the D4d forms, which are produced by rotation around the W-W bond by ±45°. It is therefore concluded that the gas-phase transition state becomes a minimum on the potential energy surface when subjected to crystal packing in the solid-state.

f-Element Half-Sandwich Complexes: A Tetrasilylcyclobutadienyl-Uranium(IV)-Tris(tetrahydroborate) Anion Pianostool Complex.

Despite there being numerous examples of f-element compounds supported by cyclopentadienyl, arene, cycloheptatrienyl, and cyclooctatetraenyl ligands (C5-8 ), cyclobutadienyl (C4 ) complexes remain exceedingly rare. Here, we report that reaction of [Li2 {C4 (SiMe3 )4 }(THF)2 ] (1) with [U(BH4 )3 (THF)2 ] (2) gives the pianostool complex [U{C4 (SiMe3 )4 }(BH4 )3 ][Li(THF)4 ] (3), where use of a borohydride and preformed C4 -unit circumvents difficulties in product isolation and closing a C4 -ring at uranium. Complex 3 is an unprecedented example of an f-element half-sandwich cyclobutadienyl complex, and it is only the second example of an actinide-cyclobutadienyl complex, the other being an inverse-sandwich. The U-C distances are short (av. 2.513 Å), reflecting the formal 2- charge of the C4 -unit, and the SiMe3 groups are displaced from the C4 -plane, which we propose maximises U-C4 orbital overlap. DFT calculations identify two quasi-degenerate U-C4 π-bonds utilising the ψ2 and ψ3 molecular orbitals of the C4 -unit, but the potential δ-bond using the ψ4 orbital is vacant.

A phase I trial of MK-2206 and hydroxychloroquine in patients with advanced solid tumors.

PURPOSE: Given the evidence that coordinate inhibition of AKT induces autophagy, we studied the combination of the AKT inhibitor, MK-2206 with hydroxychloroquine (HCQ) in patients with advanced solid tumors. METHODS: Patients were treated with weekly MK-2206 (135 mg or 200 mg) plus HCQ (200 mg, 400 mg or 600 mg BID). RESULTS: Thirty-five patients were enrolled across 5 dose levels. Two DLTs of grade 3 maculo-papular rash were observed at dose level 2 (MK-2206 200 mg weekly plus HCQ at 400 mg BID) and 1 DLT of grade 3 fatigue at dose level 2B (MK-2206 135 mg weekly plus HCQ 600 mg BID). The maximum tolerated dose (MTD) was declared as dose level 2B. The most common adverse events attributed to MK-2206 were hyperglycemia (N = 18; 51%), fatigue (N = 17; 49%), maculo-papular rash (N = 16; 46%), diarrhea (N = 12; 34%), anorexia (N = 11; 31%), and nausea (N = 11; 31%). Patients experiencing adverse events attributed to HCQ were small in number (N = 13) and primarily included fatigue (N = 5; 14%) and maculo-papular rashes (N = 3; 9%). Statistically significant effects on the pharmacokinetic properties of MK-2206 were observed in combination with HCQ. In addition, the plasma concentrations of HCQ in the combination with MK-2206 were significantly higher than the plasma levels of HCQ as monotherapy in prior studies. The best overall response of stable disease was observed in 5/34 (15%) patients. CONCLUSION: The combination of MK-2206 and hydroxychloroquine was tolerable, but with substantial number of drug-related AEs and minimal evidence of antitumor activity.

Phase II California Cancer Consortium Trial of Gemcitabine-Eribulin Combination in Cisplatin-Ineligible Patients With Metastatic Urothelial Carcinoma: Final Report (NCI-9653).

PURPOSE: Patients with metastatic urothelial carcinoma are often ineligible for cisplatin-based treatments. A National Cancer Institute Cancer Therapy Evaluation Program-sponsored trial assessed the tolerability and efficacy of a gemcitabine-eribulin combination in this population. METHODS: Patients with treatment-naïve advanced or recurrent metastatic urothelial carcinoma of the bladder, ureter, or urethra not amenable to curative surgery and not candidates for cisplatin-based therapy were eligible. Cisplatin ineligibility was defined as creatinine clearance less than 60 mL/min (but ≥ 30 mL/min), grade 2 neuropathy, or grade 2 hearing loss. Treatment was gemcitabine 1,000 mg/m2 intravenously followed by eribulin 1.4 mg/m2, both on days 1 and 8, repeated in 21-day cycles until progression or unacceptable toxicity. A Simon two-stage phase II trial design was used to distinguish between Response Evaluation Criteria in Solid Tumors, version 1.1 objective response rates of 20% versus 50%. RESULTS: Between June 2015 and March 2017, 24 eligible patients with a median age of 73 years (range, 62 to 88 years) underwent therapy. Performance status of 0, 1, or 2 was seen in 11, 11, and two patients, respectively. Sites of disease included: lymph nodes, 16; lungs, nine; liver, seven; bladder, five; bones, two. Median number of cycles received was four (range, one to 16). Of 24 patients, 12 were confirmed responders; the observed objective response rate was 50% (95% CI, 29% to 71%). Median overall survival was 11.9 months (95% CI, 5.6 to 20.4 months), and median progression-free survival was 5.3 months (95% CI, 4.5 to 6.7 months). The most common treatment-related any-grade toxicities were fatigue (83% of patients), neutropenia (79%), anemia (63%), alopecia (50%), elevated AST (50%), and constipation, nausea, and thrombocytopenia (42% each). CONCLUSION: Gemcitabine-eribulin treatment response and survival for cisplatin-ineligible patients compare favorably to other regimens. Additional research is needed.

Back-bonding between an electron-poor, high-oxidation-state metal and poor π-acceptor ligand in a uranium(V)-dinitrogen complex.

A fundamental bonding model in coordination and organometallic chemistry is the synergic, donor-acceptor interaction between a metal and a neutral π-acceptor ligand, in which the ligand σ donates to the metal, which π back-bonds to the ligand. This interaction typically involves a metal with an electron-rich, mid-, low- or even negative oxidation state and a ligand with a π* orbital. Here, we report that treatment of a uranium-carbene complex with an organoazide produces a uranium(V)-bis(imido)-dinitrogen complex, stabilized by a lithium counterion. This complex, which was isolated in a crystalline form, involves an electron-poor, high-oxidation-state uranium(V) 5f1 ion that is π back-bonded to the poor π-acceptor ligand dinitrogen. We propose that this is made possible by a combination of cooperative heterobimetallic uranium-lithium effects and the presence of suitable ancillary ligands that render the uranium ion unusually electron rich. This electron-poor back-bonding could have implications for the field of dinitrogen activation.

Selumetinib in paediatric patients with BRAF-aberrant or neurofibromatosis type 1-associated recurrent, refractory, or progressive low-grade glioma: a multicentre, phase 2 trial.

BACKGROUND: Paediatric low-grade glioma is the most common CNS tumour of childhood. Although overall survival is good, disease often recurs. No single universally accepted treatment exists for these patients; however, standard cytotoxic chemotherapies are generally used. We aimed to assess the activity of selumetinib, a MEK1/2 inhibitor, in these patients. METHODS: The Pediatric Brain Tumor Consortium performed a multicentre, phase 2 study in patients with paediatric low-grade glioma in 11 hospitals in the USA. Patients aged 3-21 years with a Lansky or Karnofsky performance score greater than 60 and the presence of recurrent, refractory, or progressive paediatric low-grade glioma after at least one standard therapy were eligible for inclusion. Patients were assigned to six unique strata according to histology, tumour location, NF1 status, and BRAF aberration status; herein, we report the results of strata 1 and 3. Stratum 1 comprised patients with WHO grade I pilocytic astrocytoma harbouring either one of the two most common BRAF aberrations (KIAA1549-BRAF fusion or the BRAFV600E [Val600Glu] mutation). Stratum 3 comprised patients with any neurofibromatosis type 1 (NF1)-associated paediatric low-grade glioma (WHO grades I and II). Selumetinib was provided as capsules given orally at the recommended phase 2 dose of 25 mg/m2 twice daily in 28-day courses for up to 26 courses. The primary endpoint was the proportion of patients with a stratum-specific objective response (partial response or complete response), as assessed by the local site and sustained for at least 8 weeks. All responses were reviewed centrally. All eligible patients who initiated treatment were evaluable for the activity and toxicity analyses. Although the trial is ongoing in other strata, enrolment and planned follow-up is complete for strata 1 and 3. This trial is registered with ClinicalTrials.gov, number NCT01089101. FINDINGS: Between July 25, 2013, and June 12, 2015, 25 eligible and evaluable patients were accrued to stratum 1, and between Aug 28, 2013, and June 25, 2015, 25 eligible and evaluable patients were accrued to stratum 3. In stratum 1, nine (36% [95% CI 18-57]) of 25 patients achieved a sustained partial response. The median follow-up for the 11 patients who had not had a progression event by Aug 9, 2018, was 36·40 months (IQR 21·72-45·59). In stratum 3, ten (40% [21-61]) of 25 patients achieved a sustained partial response; median follow-up was 48·60 months (IQR 39·14-51·31) for the 17 patients without a progression event by Aug 9, 2018. The most frequent grade 3 or worse adverse events were elevated creatine phosphokinase (five [10%]) and maculopapular rash (five [10%]). No treatment-realted deaths were reported. INTERPRETATION: Selumetinib is active in recurrent, refractory, or progressive pilocytic astrocytoma harbouring common BRAF aberrations and NF1-associated paediatric low-grade glioma. These results show that selumetinib could be an alternative to standard chemotherapy for these subgroups of patients, and have directly led to the development of two Children's Oncology Group phase 3 studies comparing standard chemotherapy to selumetinib in patients with newly diagnosed paediatric low-grade glioma both with and without NF1. FUNDING: National Cancer Institute Cancer Therapy Evaluation Program, the American Lebanese Syrian Associated Charities, and AstraZeneca.

Bimetallic Cooperative Cleavage of Dinitrogen to Nitride and Tandem Frustrated Lewis Pair Hydrogenation to Ammonia.

Although reductive cleavage of dinitrogen (N2 ) to nitride (N3- ) and hydrogenation with dihydrogen (H2 ) to yield ammonia (NH3 ) is accomplished in heterogeneous Haber-Bosch industrial processes on a vast scale, sequentially coupling these elementary reactions together with a single metal complex remains a major challenge for homogeneous molecular complexes. Herein, we report that the reaction of a chloro titanium triamidoamine complex with magnesium effects complete reductive cleavage of N2 to give a dinitride dititanium dimagnesium ditriamidoamine complex. Tandem H2 splitting by a phosphine-borane frustrated Lewis pair (FLP) shuttles H atoms to the N3- , evolving NH3 . Isotope labelling experiments confirmed N2 and H2 fixation. Though not yet catalytic, these results give unprecedented insight into coupling N2 and H2 cleavage and N-H bond formation steps together, highlight the importance of heterobimetallic cooperativity in N2 activation, and establish FLPs in NH3 synthesis.

Reversible coordination of N2 and H2 to a homoleptic S = 1/2 Fe(i) diphosphine complex in solution and the solid state.

The synthesis and characterisation of the S = 1/2 Fe(i) complex [Fe(depe)2]+[BArF4]- ([1]+[BArF4]-), and the facile reversible binding of N2 and H2 in both solution and the solid state to form the adducts [1·N2]+ and [1·H2]+, are reported. Coordination of N2 in THF is thermodynamically favourable under ambient conditions (1 atm; ΔG 298 = -4.9(1) kcal mol-1), while heterogenous binding is more favourable for H2 than N2 by a factor of ∼300. [1·H2]+[BArF4]- represents a rare example of a well-defined, open-shell, non-classical dihydrogen complex, as corroborated by ESR spectroscopy. The rapid exchange between N2 and H2 coordination under ambient conditions is unique for a paramagnetic Fe complex.

Catalytic Dinitrogen Reduction to Ammonia at a Triamidoamine-Titanium Complex.

Catalytic reduction of N2 to NH3 by a Ti complex has been achieved, thus now adding an early d-block metal to the small group of mid- and late-d-block metals (Mo, Fe, Ru, Os, Co) that catalytically produce NH3 by N2 reduction and protonolysis under homogeneous, abiological conditions. Reduction of [TiIV (TrenTMS )X] (X=Cl, 1A; I, 1B; TrenTMS =N(CH2 CH2 NSiMe3 )3 ) with KC8 affords [TiIII (TrenTMS )] (2). Addition of N2 affords [{(TrenTMS )TiIII }2 (µ-η1 :η1 -N2 )] (3); further reduction with KC8 gives [{(TrenTMS )TiIV }2 (µ-η1 :η1 :η2 :η2 -N2 K2 )] (4). Addition of benzo-15-crown-5 ether (B15C5) to 4 affords [{(TrenTMS )TiIV }2 (µ-η1 :η1 -N2 )][K(B15C5)2 ]2 (5). Complexes 3-5 treated under N2 with KC8 and [R3 PH][I], (the weakest H+ source yet used in N2 reduction) produce up to 18 equiv of NH3 with only trace N2 H4 . When only acid is present, N2 H4 is the dominant product, suggesting successive protonation produces [{(TrenTMS )TiIV }2 (µ-η1 :η1 -N2 H4 )][I]2 , and that extruded N2 H4 reacts further with [R3 PH][I]/KC8 to form NH3 .

A Phase II Trial of Neoadjuvant MK-2206, an AKT Inhibitor, with Anastrozole in Clinical Stage II or III PIK3CA-Mutant ER-Positive and HER2-Negative Breast Cancer.

Purpose: Hyperactivation of AKT is common and associated with endocrine resistance in estrogen receptor-positive (ER+) breast cancer. The allosteric pan-AKT inhibitor MK-2206 induced apoptosis in PIK3CA-mutant ER+ breast cancer under estrogen-deprived condition in preclinical studies. This neoadjuvant phase II trial was therefore conducted to test the hypothesis that adding MK-2206 to anastrozole induces pathologic complete response (pCR) in PIK3CA mutant ER+ breast cancer.Experimental Design: Potential eligible patients with clinical stage II/III ER+/HER2- breast cancer were preregistered and received anastrozole (goserelin if premenopausal) for 28 days in cycle 0 pending tumor PIK3CA sequencing. Patients positive for PIK3CA mutation in the tumor were eligible to start MK-2206 (150 mg orally weekly, with prophylactic prednisone) on cycle 1 day 2 (C1D2) and to receive a maximum of four 28-day cycles of combination therapy before surgery. Serial biopsies were collected at preregistration, C1D1 and C1D17.Results: Fifty-one patients preregistered and 16 of 22 with PIK3CA-mutant tumors received study drug. Three patients went off study due to C1D17 Ki67 >10% (n = 2) and toxicity (n = 1). Thirteen patients completed neoadjuvant therapy followed by surgery. No pCRs were observed. Rash was common. MK-2206 did not further suppress cell proliferation and did not induce apoptosis on C1D17 biopsies. Although AKT phosphorylation was reduced, PRAS40 phosphorylation at C1D17 after MK-2206 persisted. One patient acquired an ESR1 mutation at surgery.Conclusions: MK-2206 is unlikely to add to the efficacy of anastrozole alone in PIK3CA-mutant ER+ breast cancer and should not be studied further in the target patient population. Clin Cancer Res; 23(22); 6823-32. ©2017 AACR.

Cationic silyldiazenido complexes of the Fe(diphosphine)2(N2) platform: structural and electronic models for an elusive first intermediate in N2 fixation.

The first cationic Fe silyldiazenido complexes, [Fe(PP)2(NN-SiMe3)]+[BArF4]- (PP = dmpe/depe), have been synthesised and thoroughly characterised. Computational studies show the compounds to be useful structural and electronic surrogates for the more elusive [Fe(PP)2(NN-H)]+, which are postulated intermediates in the H+/e- mediated fixation of N2 by Fe(PP)2(N2) species.

Selective Catalytic Reduction of N2 to N2H4 by a Simple Fe Complex.

The catalytic fixation of N2 by molecular Fe compounds is a rapidly developing field, yet thus far few complexes can effect this transformation, and none are selective for N2H4 production. Herein we report that the simple Fe(0) complex Fe(Et2PCH2CH2PEt2)2(N2) (1) is an efficient catalyst for the selective conversion of N2 (>25 molecules N2 fixed) into N2H4, attendant with the production of ca. one molecule of NH3. Notably, the reductant (CoCp*2) and acid (Ph2NH2OTf) used are considerably weaker than conventional chemical H+ and e- sources used in previous demonstrations of N2 turnover by synthetic Fe compounds. These results show that the direct catalytic conversion of N2 to the hydrazine oxidation state on molecular Fe complexes is viable and that the mechanism of NH3 formation by such systems may proceed via Fe-N2H4 intermediates.

Teaching old compounds new tricks: efficient N2 fixation by simple Fe(N2)(diphosphine)2 complexes.

The Fe(0) species Fe(N2)(dmpe)2 exists in equilibrium with the previously unreported dimer, [Fe(dmpe2)2(µ-N2)]. For the first time these complexes, alongside Fe(N2)(depe)2, are shown unambiguously to produce N2H4 and/or NH3 upon addition of triflic acid; for Fe(N2)(depe)2 this represents one of the highest electron conversion efficiencies for Fe complexes to date.

SU2C phase Ib study of paclitaxel and MK-2206 in advanced solid tumors and metastatic breast cancer.

BACKGROUND: There is preclinical synergism between taxanes and MK-2206. We aim to determine the maximum tolerated dose, safety, and activity of combining MK-2206 and paclitaxel in metastatic cancer. METHODS: Patients received weekly doses of paclitaxel at 80mg/m2 on day 1, followed by MK-2206 orally on day 2 escalated at 90mg, 135mg, and 200mg. Treatment continued until progression, excessive toxicity, or patient request. Blood and tissue were collected for pharmacokinetic and pharmacodynamics markers. A cycle consisted of three weeks of therapy. Dose-limiting toxicity (DLT) was defined as unacceptable toxicity during the first cycle. All statistical tests were two-sided. RESULTS: Twenty-two patients were treated, nine in dose escalation and 13 in dose expansion. Median age was 55 years. Median number of cycles was four. Dose escalation was completed with no DLT. CTCAE Grade 3 or higher adverse events were fatigue (n = 2), rash (n = 2), hyperglycemia (n = 1), and neutropenia (n = 7). Four patients in the expansion phase required MK-2206 dose reduction. Phase II recommended dose was established as paclitaxel 80mg/m2 weekly on day 1, and MK-2206 135mg weekly on day 2. Paclitaxel systemic exposure was similar in the presence or absence of MK-2206. Plasma MK-2206 concentrations were similar to data from previous phase I monotherapy. There was a statistically significant decrease in expression of pAKT S473 (P = .01) and pAKT T308 (P = .002) after therapy. PI3K/AKT/mTOR downregulation in tumor tissues and circulating markers did not correlate with tumor response or clinical benefit. There were five objective responses, and nine patients had stable disease. CONCLUSION: MK-2206 was well tolerated with paclitaxel. Preliminary antitumor activity was documented.

Bypassing a highly unstable frustrated Lewis pair: dihydrogen cleavage by a thermally robust silylium-phosphine adduct.

The thermally robust silylium complex [iPr3Si-PtBu3](+)[B(C6F5)4](-) (1) activates H2/D2 at 90 °C (PhCl); no evidence for dissociation into the separated Lewis pair is found. DFT calculations show H2 cleavage proceeds via Si-P bond elongation to form an encounter complex directly from the adduct, thus avoiding the non-isolable iPr3Si(+)-PtBu3 FLP.

A Convenient Synthetic Protocol to 1,2-Bis(dialkylphosphino)ethanes.

1,2-Bis(dialkylphosphino)ethanes are readily prepared from the parent phosphine oxides, via a novel sodium aluminium hydride/sodium hydride reduction protocol of intermediate chlorophosphonium chlorides. This approach is amenable to multi-gram syntheses, utilises readily available and inexpensive reagents, and benefits from a facile non-aqueous work-up in the final reductive step.