Organophotocatalytic Remote Thiocyanation Reaction via Ring-Opening Functionalization of Cycloalkanols.

The remote C(sp3)-SCN bond formation via ring-opening functionalization of cycloalkanols with N-thiocyanatosaccharin as the precursor of SCN radicals and pyrylium salt as the organic photocatalyst under visible light has been developed. Thus, various terminal keto thiocyanates were prepared without transition metals and oxidants in moderate to good yields. The simplicity, wide substrate scope and mild conditions feature its synthetic application capability.

Me3SiBr-promoted cascade electrophilic thiocyanation/cyclization of ortho-alkynylanilines to synthesize indole derivatives.

A Lewis acid-promoted electrophilic thiocyanation/cyclization of ortho-alkynylanilines for the synthesis of indole derivatives has been developed. The reaction utilizes Me3SiBr as the Lewis acid and N-thiocyanatosuccinimide as the thiocyanation reagent. A series of 2-aryl-3-thiocyanato indoles were prepared in moderate to high yields under mild conditions without metals and oxidants. It provides an efficient protocol for the construction of the indole skeleton and C-SCN and C-N bonds in one step as well.

Copper(I)-catalyzed electrophilic thiocyanation/dearomatization/spirocyclization of benzofurans to synthesize benzannulated spiroketals.

A Lewis acid-catalyzed electrophilic dearomatizative thiocyanation and cyclization of benzofurans with N-thiocyanatosuccinimide has been accomplished by Lewis acid catalysis with CuOTf under mild conditions. It was suggested that the electrophilic thiocyanating reagent was activated by CuOTf, and difunctionalization was achieved through a thiocyanation/spirocyclization pathway. Thus, a series of thiocyanato-containing spiroketals were obtained in moderate to high yields. It provides an alternative approach for the synthesis of functionalized [6,5]/[5,5]-spiroketals.

Synthesis of thiocyanato-containing phenanthrenes and dihydronaphthalenes via Lewis acid-activated tandem electrophilic thiocyanation/carbocyclization of alkynes.

A tandem electrophilic thiocyanation and cyclization of arene-alkynes has been developed under mild conditions, affording thiocyanato-substituted phenanthrenes, dihydronaphthalenes, 2H-chromenes and dihydroquinolines in moderate to excellent yields. This reaction provides an efficient protocol for the construction of C-SCN and C-C bonds in one step. In this transformation, N-thiocyanato reagent serves as a convenient precursor to transfer SCN+ in the presence of trimethylchlorosilane, and the cyclization exhibited exclusive 6-endo-dig selectivity. Finally, a gram scale reaction and further derivatizations highlight the utility of this synthetic strategy.

Electrophilic Thiocyanato Reagent Assisted Oxa-Michael/Thiocyanation of α,ß-Unsaturated Ketones.

A route for thiocyanation-functionalization of the electron-deficient C═C double bond was developed. Regioselective thiocyanation-etherification of α,ß-unsaturated ketones was achieved. The desired products were obtained in moderate to high yields under mild conditions. It was suggested that the nucleophile was activated by the electrophilic thiocyanato reagent, and difunctionalization was achieved through a 1,4-addition/thiocyanation pathway.

Atom-Economical Thiocyanation-Amination of Alkynes with N-Thiocyanato-Dibenzenesulfonimide.

A highly regioselective protocol for intermolecular thiocyanation-amination of alkynes by N-thiocyano-dibenzenesulfonimide (NTSI) as the SCN and nitrogen sources has been developed. A C-S bond and C-N bond are simultaneously constructed in only one step. The reaction under simple mild conditions features a broad substrate scope, atom economy, high yields (up to 94%), and excellent functional group tolerance.

Lewis Acid-Catalyzed Asymmetric Selenocyanation of ß-Ketoesters with N-Selenocyanatosaccharin.

The first electrophilic asymmetric selenocyanation has been achieved in the presence of Ni(OTf)2 and (R,R)-DBFOX/Ph using N-selenocyanatosaccharin as the new selenocyanation reagent. Thus, a series of α-selenocyanato-ß-keto esters were synthesized with high yields (up to 99%) and good ee values (up to 92% ee). The readily preparation of the reagent and high enantioselectivity make this methodology much practical for the synthesis of chiral selenocyanates.

Organocatalyzed Asymmetric α-Thiocyanation of Oxindoles: Synthesis of Chiral Tertiary 3-Thiocyanatoxindoles.

An enantioselective thiocyanation of oxindoles has been developed for the first time using a bifunctional cinchona-derived organo-catalyst and N-thiocyanatophthalimide as the electrophilic thiocyanation source in the presence of 2-naphthol as the additive. Various enantioenriched 3,3'-disubstituted oxindoles with SCN-containing quaternary carbon stereocenters were synthesized under mild conditions in high yields (up to 99%) and good enantioselectivities (up to 6:94 er).

N-Thiocyanato-dibenzenesulfonimide: a new electrophilic thiocyanating reagent with enhanced reactivity.

A novel electrophilic thiocyanating reagent, N-thiocyanato-dibenzenesulfonimide, was prepared and exhibited enhanced electrophilicity with a wide scope of substrates. Thus, it reacted with activated aromatics such as phenols, indoles, anilines and anisoles without a catalyst giving the corresponding thicyanate derivatives in high yields, while TfOH for unactivated arenes and hetero aromatics and Zn(OTf)2 for ketones was used as the catalyst, respectively. It is noteworthy that internal alkenes and styrenes were bifunctionalized giving 1,2-amino thiocyanates in high yields.

N-Thiocyanatosaccharin: A "Sweet" Electrophilic Thiocyanation Reagent and the Synthetic Applications.

N-Thiocyanatosaccharin (R1) was readily prepared from the sweet additive Saccharin in two steps with a 71% overall yield. By applying this new reagent to diverse nucleophiles such as benzothiophenes, indoles, oxindoles, aromatic amines, phenols, ß-keto carbonyl compounds, and aromatic ketones, a novel electrophilic thiocyanation reaction was achieved with high yields (up to 99%). The potential recycling of Saccharin, the wide scope of substrates, and the mild reaction conditions made this protocol much more practical.

Highly Enantioselective α-Cyanation with 4-Acetylphenyl Cyanate.

A highly effective asymmetric version of α-cyanation of ß-keto esters and amides was developed with a Lewis-acid catalyst. Thus, by using 10 mol % of a tridentate bisoxazoline-zinc(II) complex as the catalyst, a series of chiral nitriles containing a quaternary carbon center were obtained in excellent enantioselectivities (up to 97 % enantiomeric excess) and up to 95 % yield in the presence of 4 Šmolar sieve at room temperature. For the first time, mild and active 4-acetylphenyl cyanate was used instead of cyano-hyperiodinate as the cationic cyano source for catalytic asymmetric α-cyanation.

Enantioselective electrophilic cyanation of ß-keto amides catalysed by a cinchona organocatalyst.

An operationally simple protocol for the enantioselective electrophilic α-cyanation of ß-keto amides catalyzed by cinchona-derived catalysts has been demonstrated. The resulting products could be obtained with good to high enantioselectivities (up to 88% ee) and with excellent yields (up to 94%) by employing the mild active 4-acetylphenyl cyanate as the cationic cyano source in the catalytic asymmetric α-cyanation reaction.

Construction and Modification of Nitrogen-Rich Polycyclic Frameworks: A Promising Fused Tricyclic Host-Guest Energetic Material with Heat Resistance, High Energy, and Low Sensitivity.

The construction and modification of novel energetic frameworks to achieve an ideal balance between high energy density and good stability are a continuous pursuit for researchers. In this work, a fused [5,6,5]-tricyclic framework was utilized as the energetic host to encapsulate the oxidant molecules for the first time. A series of new pyridazine-based [5,6] and [5,6,5] fused polycyclic nitrogen-rich skeletons and their derivatives were designed and synthesized. Two strategies, amino oxidation and host-guest inclusion, were used to modify the skeleton in only one step. All compounds exhibit good comprehensive properties (Td (onset) > 200 °C, ρ > 1.85 g cm-3, Dv > 8400 m s-1, IS > 20 J, FS > 360 N). Benefiting from the pyridazine-based fused tricyclic structure with more hydrogen bonding units and larger conjugated systems, the first example of [5,6,5]-tricyclic host-guest energetic material triamino-9H-pyrazolo[3,4-d][1,2,4]triazolo[4,3-b]pyridazine-diperchloric acid (10), shows high decomposition temperature (Td (onset) = 336 °C), high density and heats of formation (ρ = 1.94 g cm-3, ΔHf = 733.4 kJ mol-1), high detonation performance (Dv = 8820 m s-1, P = 36.2 GPa), high specific impulse (Isp = 269 s), and low sensitivity (IS = 30 J, FS > 360 N). The comprehensive performance of 10 is superior to that of high-energy explosive RDX and heat-resistant explosives such as HNS and LLM-105. 10 has the potential to become a comprehensive advanced energetic material that simultaneously satisfies the requirements of high-energy and low-sensitivity explosives, heat-resistant explosives, and solid propellants. This work may give new insights into the construction and modification of a nitrogen-rich polycyclic framework and broaden the applications of fused polycyclic framework for the development of host-guest energetic materials.

AIBN-initiated direct thiocyanation of benzylic sp3 C-H with N-thiocyanatosaccharin.

Direct thiocyanations of benzylic compounds have been implemented. Here, a new strategy, involving a free radical reaction pathway initiated by AIBN, was used to construct the benzylic sp3 C-SCN bond. In this way, the disadvantage of other strategies involving introducing leaving groups in advance to synthesize benzyl thiocyanate compounds was overcome. The currently developed protocol also involved the use of readily available raw materials and resulted in high product yields (up to 100%), both being great advantages for synthesizing benzyl thiocyanates.

The Chemistry and Properties of Energetic Materials Bearing [1,2,4]Triazolo[4,3-b][1,2,4,5]tetrazine Fused Rings.

Treatment of heterocyclic amines featuring fused rings of [1,2,4]triazolo[4,3-b][1,2,4,5]tetrazine with fuming HNO3 /P2 O5 leads to six fully characterized explosives through multiple nitration and reduction or oxidation mechanism. Thus, 4-nitro-N-(3-nitro[1,2,4]triazolo[4,3-b][1,2,4,5]tetrazin-6-yl)-1,2,5-oxadiazol-3-amine (3 b, TTDNF) showed high performance (D=9180 m s-1 , P=36.7 GPa) and low impact sensitivity (IS>40 J) while N-([1,2,4]triazolo[4,3-b][1,2,4,5]tetrazin-6-yl)-3-nitro-1,2,4-oxadiazol-5-amine (4 a, TTNOA) exhibited a potential cast explosive component with low melting point at 88.2 °C and high onset decomposition temperature at 226.2 °C.

Enantioselective Organocatalyzed Direct α-Thiocyanation of Cyclic ß-Ketoesters by N-Thiocyanatophthalimide.

A new electrophilic thiocyanation reagent, N-thiocyanatophthalimide, was synthesized and applied to the first example of catalytic asymmetric electrophilic α-thiocyanation of various cyclic ß-ketoesters by the bifunctional cinchona alkaloid catalysis. Thus, a variety of chiral α-thiocyanato ß-ketoesters with a quaternary carbon center have been achieved in excellent yields (up to 99%) and high enantioselectivities (up to 94% ee) in a convenient manner.

A novel polyaspartic acid derivative with multifunctional groups for scale inhibition application.

Polyaspartic acid is a green biodegradable antiscalant and widely applied in water treatment field. However, its scale inhibition efficiency is not prominent, especially for calcium orthophosphate. So we introduced acylamino and hydroxyl groups simultaneously to prepare a novel polyaspartic-acid derivative (PASPTU) with multifunctional groups by the reaction of polysuccinimide with threonine and urea. The graft copolymer was analyzed by using nuclear magnetic resonance, gel permeation chromatography, thermogravimetric analyzer and Fourier transform infrared spectroscopy. Its scale inhibition performance for calcium orthophosphate, calcium sulfate and calcium carbonate was evaluated. The findings showed that the scale inhibition rates of the graft copolymer reached up to 100% for calcium orthophosphate, 100% for calcium sulfate and 91% for calcium carbonate at certain dosages. The findings above showed that the copolymer had excellent scale inhibition efficiency for calcium salts in water treatment processes.

Cyanotetrazolylborohydride (CTB) anion-based ionic liquids with low viscosity and high energy capacity as ultrafast-igniting hypergolic fuels.

A series of hypergolic cyanotetrazolylborohydride (CTB) anion-based ionic liquids have been synthesized by a straightforward N-hydroboration of tetrazole followed by a salt metathesis reaction, which exhibited remarkably low viscosity (<20 mPa s), high density (often >1.1 g cm-3), and ultra-short ignition delay time (as short as 1.4 ms) upon contact with white fuming nitric acid (WFNA).

Catalytic Asymmetric Electrophilic Cyanation of 3-Substituted Oxindoles.

The first example of catalytic asymmetric electrophilic cyanation of 3-substituted oxindoles has been achieved using readily accessible 4-acetylphenyl cyanate as the cyano source. Thus, a series of all-carbon quaternary center 3-aryl-3-cyano oxindoles were prepared using a zinc complex of a chiral pincer ligand as the catalyst in high yields (up to 95%) and excellent enantioselectivities (up to >99% ee) in the presence of 4 Å MS and 2,6-lutidine in THF at 0 °C.

Eremophilane sesquiterpenes from Hawaiian endophytic fungus Chaetoconis sp. FT087.

Seven sesquiterpene derivatives, including chaetopenoids A-F and dendryphiellin A1, and 6-methyl-(2E, 4E, 6S) octadienoic acid were isolated from the culture broth of Chaetoconis sp. FT087. Their structures were determined through the analysis of HRMS and NMR spectroscopic data. The absolute configurations of chaetopenoids A-D were elucidated by comparison of their CD and optical rotation data with those in the literature. Chaetopenoids A-C and E belong to the eremophilane type of sesquiterpenoids, while chaetopenoids D and F and dendryphiellin A1 have a trinor-eremophilane skeleton. All compounds were tested against A2780 and cisplatin resistant A2780CisR cell lines, and dendryphiellin A1 was moderately active with IC50 values of 6.6 and 9.1 µg/mL, respectively.