Efficient synthesis of diborylalkenes from alkenes and diboron by a new PSiP-pincer palladium-catalyzed dehydrogenative borylation

The efficient synthesis of various diborylalkenes such as 1,1-, trans-1,2-, and cyclic 1,2-diborylalkenes from alkenes and diboron was achieved for the first time. Selective preparation of di- and monoborylalkenes was also realized by the appropriate choice of reaction conditions. The reaction was found to proceed via a new mechanism of dehydrogenative borylation through a monoborylpalladium complex bearing an anionic PSiP-pincer ligand as a key intermediate, which realized the efficient borylation without sacrificial hydroboration or hydrogenation of the alkene.     

InCl3 mediated one-pot synthesis of indol-3-yl pyridine and 2,2′-bipyridine derivatives through multi-component reaction

A simple protocol for the efficient preparation of 2-(1H-Indol-3-yl)-6-methoxy-4-aryl pyridine-3,5-dicarbonitrile and 6-methoxy-4-aryl-2,2′-bipyridine-5-carbonitrile derivatives has been achieved through one-pot multi-component reaction under reflux condition. Particularly valuable features of this method include high yields of products in short reaction time and broad substrate scope. It is an efficient and promising synthetic strategy to build indol-3-yl pyridine and 2,2′-bipyridine skeletons.     

Palladium-catalyzed cascade synthesis of spirocyclic oxindoles via regioselective C2-H arylation and C8-H alkylation of naphthalene ring

A simultaneous C2-H arylation and C8-H alkylation of naphthalene ring has been achieved by palladiumcatalyzed cascade reaction of N-(2-halophenyl)-2-(naphthalen-1-yl)acrylamides with aryl iodides,which provides an efficient method for synthesizing various aryl-substituted spirocyclic oxindoles.The protocol enables three C-C bonds formation via an intramolecular Heck reaction and sequentially regioselective C-H bond activation.     

Development and application of a direct vinyl lithiation of cis-stilbene and a directed vinyl lithiation of an unsymmetrical cis-stilbene

[reaction: see text] The vinyl deprotonation of cis-stilbene can be readily achieved using s-BuLi in THF at -25 degrees C. The generated 1-lithio-1,2-diphenylethene undergoes an in situ Z-to-E isomerization, and subsequent reaction with electrophiles results in an efficient stereoselective synthesis of trisubstituted alkenes. A directed vinyl lithiation of the unsymmetrical cis-stilbene 2-styryl-phenyl-carbamic acid tert-butyl ester can be achieved regioselectively, thereby expanding this methodology for further synthetic applications in indole chemistry.     

Rapid biomimetic total synthesis of (±)-rossinone B

A biomimetic total synthesis of (±)-rossinone B has been achieved through a highly efficient strategy featuring a series of rationally designed reactions, including a one-pot allylic rearrangement/oxidation reaction to generate the vinyl quinone 27, an intramolecular vinyl quinone Diels-Alder reaction to construct the linear 6-6-5 tricyclic core of 28, and a double conjugate addition/β-elimination cascade to complete the total synthesis of 1.     

1-芳基-2-丙酮的合成研究

以芳香胺为原料, 经重氮化和改进的Meerwein芳基取代反应, 合成了一系列的1-芳基-2-丙酮, 其中1-(3,5-二三氟甲基苯基)-2-丙酮是一个新化合物. 改进后的方法简化了合成步骤, 提高了收率, 可方便地用于在苯环上具有不同取代基的芳基丙酮的合成.     

Chemoenzymatic synthesis of duloxetine and its enantiomer: lipase-catalyzed resolution of 3-hydroxy-3-(2-thienyl) propanenitrile

An efficient and facile chemoenzymatic synthesis of duloxetine by lipase mediated resolution of 3-hydroxy-3-(2-thienyl)propanenitrile has been achieved. This process also describes an enantioconvergent synthesis of duloxetine via a Mitsunobu reaction.     

Organocatalytic synthesis of (2S,3R)-3-hydroxy-3-methyl-proline (OHMePro), a component of polyoxypeptins, and relatives using OHMePro itself as a catalyst

An efficient synthesis of (2S,3R)-3-hydroxy-3-methylproline (OHMePro), a component of polyoxypeptins, and relatives was achieved, in which an intramolecular asymmetric aldol reaction of the ketoaldehyde using OHMePro itself as an organocatalyst constitutes a key step.     

Total synthesis of (+)-nafuredin-γ using a highly stereoselective Ti-mediated aldol reaction

An efficient total synthesis of (+)-nafuredin-γ has been achieved in 10 steps from (E)-3-(tributylstannyl)propenal. The synthesis features direct construction of an anti-1,2-diol moiety via a Ti-mediated aldol reaction of lactyl derivative and rapid fragment assembly, which relied on well-established Pd chemistry.     

Total synthesis of (+/-)-stemodinone via an efficient ring-exchange strategy

A total synthesis of (+/-)-stemodinone, a tetracyclic stemodane diterpene, from the known tricyclic methyl olefin 11 is described. The key steps involve an efficient ring-exchange reaction and palladium(0)-catalyzed lactone migration. The ring-exchange strategy for controlling the stereochemistry was based on an initial Diels-Alder reaction to form a new ring followed by cleavage of the original ring. Cleavage of the original ring of the Diels-Alder adduct 9 was achieved by an initial regio- and chemoselective Baeyer-Villiger oxidation followed by the Pd(0)-catalyzed lactone-migration reaction reported by us.     

A short, efficient, and stereoselective total synthesis of a pyrrolidine alkaloid: (-)-codonopsinine

An efficient total synthesis of antibiotic (-)-codonopsinine 1 with an overall yield of 44% was achieved from d-alanine as a chiral template. The key steps in our strategy are modified Sharpless asymmetric dihydroxylation reaction and the highly stereoselective intramolecular acid-catalyzed amidocyclization.     

Lithium Ephedrinate Mediated Aldol Reaction of Arylacetonitriles: Thermodynamic Control of Enantioselectivity

Deracemization , the conversion of a racemic mixture into an enantiomerically enriched material, is achieved with the retro-aldol reaction of rac- 1 in the presence of lithium (−)-ephedrinate [Eq. (1)]. Remarkably, two stereogenic centers are simultaneously deracemized. This reaction shows that efficient thermodynamic control of the enantioselectivity of aldol reactions is possible     

An efficient synthesis of 2,2-bis(1H-indol-3-yl)-2H-acenaphthen-1-one catalyzed by recyclable solid superacid SO_4~(2-)/TiO_2 under grinding condition

<正>An efficient synthesis of symmetrical 2,2-bis(1H-indol-3-yl)-2H-acenaphthen-1-one is achieved via a reaction of acenaphthe-nequinone and indoles catalyzed by solid superacid SO_4~(2-)/TiO_2 under solvent-free conditions at room temperature by grinding, which provides an efficient route to the synthesis of symmetrical 2,2-bis(1H-indol-3-yl)-2H-acenaphthen-1-one.This procedure offers several advantages including solvent-free conditions,excellent yields of products,simple work-up as well as reuse of catalysts which makes it a useful and attractive protocol for the synthesis of these compounds.     

Efficient synthesis of isofagomine and noeuromycin

Starting from D-arabinose the synthesis of the very strong glycosidase inhibitors isofagomine (2) and noeuromycin (3) was achieved in six and seven steps, respectively. Keystep in the reaction sequence is the application of an efficient C-4 oxidation method to benzyl alpha-D-arabino-pyranoside. Subsequent Henry reaction of the obtained aldoketose with nitromethane provided the required branched carbohydrate precursors, which gave access to 2 and 3 in 17-21% overall yield.     

A facile synthesis of novel 1,4-benzoxazepin-2-one derivatives

An efficient and simple synthesis of 1,4-benzoxazepin-2-one derivatives has been achieved via the reaction of isoquinoline, activated acetylenes, and 1-(6-hydroxy-2-isopropenyl-1-benzofuran-yl)-1-ethanone in water without using any catalyst. This one-pot reaction occurs in high yields under mild conditions.     

Synthesis of ent-thallusin

[reaction: see text] A three-step route from sclareol oxide (6) to bromo ester 4 in 53% overall yield was achieved using the efficient oxidation of an allylic bromide to an enal with bis(2,4,6-trimethylpyridine)silver(I) hexafluorophosphate in DMSO. Stille coupling of bromo ester 4 with stannylpyridine 5 gave the trimethyl ester of ent-thallusin in 54-92% yield by the stoichiometric conversion of 4 to a vinyl palladium intermediate prior to the addition of 5 to the reaction.     

A rapid and green method for expedient multicomponent synthesis of N-substituted decahydroacridine-1,8-diones as potential antimicrobial agents

Research on Chemical Intermediates - An efficient, green, high yielding, and quick method for the synthesis of N-substituted decahydroacridine-1,8-diones was achieved by multicomponent reaction...     

A fast radical chain mechanism in the polyfluoroalkoxylation of aromatics through NO2 group displacement. Mechanistic and theoretical studies

Introduction of polyfluoroalkoxy and polyfluoroalkylthio substituents in aromatic rings can be achieved with mild conditions and short times thorough reaction of concentrated solutions of dinitrobenzenes in DMF with polyfluoro alcohols and polyfluoro thiols in moderate excess, in the presence of excess tetrabutylammonium fluoride as a base. Mechanistic studies suggest that under these conditions a fast radical chain mechanism operates. This mechanism is elicited by oxidation of a Meisenheimer complex and proceeds through a radical aromatic substitution with the polyfluoroalkoxy or the polyfluoroalkylthio radicals as key intermediates. At low concentrations, entrainment can be achieved with superoxide anion. A rationale for this effect is discussed. Answers to particular questions about the proposed mechanism are achieved through a theoretical study at the B3LYP/6-31+G(d,p) level. Specifically, the competition between the radical mechanism and the corresponding polar one (classical S(N)Ar reaction) is studied in that way, with the conclusion that the key steps of the radical mechanism in our reaction conditions (polar aprotic solvent) are at least as efficient as the ones of the polar one, thus justifying the observed kinetic advantage for the chain reaction in the conditions where an efficient initiation occurs.     

One-pot synthesis of 12H-benzo[b]xanthen-12-ones and naphtha[2,3-b]furans from non-naphthalene substrates

An efficient one-pot synthesis of 12H-benzo[b]xanthen-12-ones via an oxidant initiated and base promoted tandem reaction of 2-(4-(2-haloaryl)-4-hydroxybut-1-ynyl)benzaldehydes has been developed. By using similar strategy, a one-pot synthesis of naphtha[2,3-b]furans from the cascade reaction of 2-(4-hydroxy-but-1-ynyl)benzaldehydes with 2-bromoacetonitrile or α-bromocarbonyl compounds has also been achieved.     

An efficient synthesis of the C27–C45 fragment of lagunamide A,a cyclodepsipeptide with potent cytotoxic and antimalarial properties

An efficient and stereoselective synthesis of the entire C27–C45 moiety of lagunamide A has been achieved from 1-[(4S)-4-benzyl-2-thioxothiazolidin-3-yl]propan-1-one in six steps with 22% overall yield. The key step in the synthesis is an asymmetric acetal aldol reaction featuring the enantioselective addition of a chiral thiazolidinethione-derived titanium enolate to an acetal to establish the stereochemistry at C39.