Copper-catalyzed asymmetric silylative cyclization of cyclohexadienone-containing 1,6-enynes

The first copper-catalyzed asymmetric silylative cyclization of cyclohexadienone-containing 1,6-enynes has been accomplished through a tandem process: regioselective silylcupration of terminal unactivated alkynes and subsequently enantioselective conjugate addition to cyclohexadienones. This reaction proceeded smoothly to afford the cis-hydrobenzofuran and cis-hydroindole frameworks bearing two consecutive chiral carbon centers in high to excellent yields and moderate enantioselectivities. Additionally, the cyclization products could be readily subjected to several transformations for elaborating synthetic utilities.     

Highly regio- and stereoselective synthesis of 1,3-enynes from unactivated ethylenes via palladium-catalyzed cross-coupling

An efficient procedure for regio- and stereoselective synthesis of a series of conjugated enynes by a simple Pd-catalyzed cross-coupling reaction of unactivated ethylenes and ethynyl bromide has been developed. The reaction proceeds smoothly in DMF to give the corresponding products in good to excellent yields. The protocol can tolerate a broad range of functional groups on the substrates.     

Tandem one-pot synthesis of polysubstituted pyridines using the Blaise reaction intermediate and 1,3-enynes

A tandem one-pot method for the construction of a pyridine moiety with selective control of substitution patterns has been developed through the sequential reactions of nitrile with a Reformatsky reagent and 1,3-enyne involving regio- and chemoselective addition of the Blaise reaction intermediate to 1,3-enyne, followed by isomerization, cyclization, and an aromatization cascade.     

Halogenated salt assisted Cu-catalyzed asymmetric 1,4-borylstannation of 1,3-enynes: enantioselective synthesis of allenylstannes

An enantioselective 1,4-borylstannation of 1,3-enynes employed a chiral sulfoxide phosphine (SOP)/Cu complex as a catalyst, and the desired products, chiral allenylstannes, were first synthesized by asymmetric catalysis with satisfactory yields and enantioselectivies. In this protocol, a catalytic amount of additive, a halogenated salt, plays a crucial role in the success. Control experiments and theoretical studies disclosed that the four-membered ring transmetallation transition states which were stabilized by a halide anion are the key to yields and stereochemical outcomes.

An enantioselective 1,4-borylstannation of 1,3-enynes employed a chiral sulfoxide phosphine (SOP)/Cu complex as a catalyst, and the desired products, chiral allenylstannes, were first synthesized by asymmetric catalysis with satisfactory yields and enantioselectivies.     

Silaborations of 1,3-enynes - substrate controlled allene/1,3-diene selectivity

Silaboration of 1,3-enynes catalyzed by group 10 metal complexes affords 1,3-dienes with vinylborane and vinylsilane functions or 1,2-dienes with allylborane and vinylsilane functions. The type of product formed is determined by the size of the alkyne substituent.     

Catalytic asymmetric synthesis of 1,4-enynes

1,4-Enyne units are ubiquitous skeletons in biologically active molecules and natural products. Especially, they represent versatile building blocks for abundant downstream derivatizations via controllable modifications of both alkene and alkyne units independently. Recently, great efforts have been made to establish efficient protocols to achieve optically active 1,4-enynes. Considering the enormous application potential of enantioenriched 1,4-enyne units but no related review on this topic has been described, here we aim to provide a comprehensive summary on the catalytic methods established for enantioselective constructions of these intriguing skeletons. According to the reaction types, this review is divided into five parts, including asymmetric allylic substitution, asymmetric propargylic substitution, asymmetric alkynylallylic substitution, asymmetric hydroalkynylation and asymmetric 1,2-addition of alkynes to conjugated imines or ketones.     

Copper-catalyzed synthesis of vinyl sulfides

[reaction: see text] We report a method for the synthesis of vinyl sulfides using the soluble copper(I) catalyst [Cu(phen)(PPh3)2]NO3. The desired vinyl sulfides are obtained in good to excellent yields, with retention of stereochemistry. This protocol tolerates a wide variety of functional groups or substrates, is palladium-free, and does not require the use of expensive or air-sensitive additives.     

Copper-catalyzed synthesis of unsymmetrical triarylphosphines

Various triarylphosphines have been prepared by coupling diphenylphosphine with aryl iodides with catalytic amounts of CuI in the presence of either K(2)CO(3) or Cs(2)CO(3), in good yields. This method can tolerate a variety of functional groups and does not require the use of expensive additives, or harsh reaction conditions, and is palladium free.     

Copper-catalyzed one-pot synthesis of alkynylphophonates

Copper is found to be an effective catalyst for the preparation of alkynylphophonates. A novel copper-catalyzed one-pot synthesis of alkynylphophonates from terminal alkynes and dialkyl phosphites is developed which involves the haloalkynes intermediates. This method provides a unique and alternative approach to the well-documented oxidative coupling or arylpropiolic acid strategies.     

Copper-catalyzed synthesis of enantioenriched tetraarylethanes

Herein we report the asymmetric synthesis of 1,2-dipyridyl-1,2-diarylethanes via an unusual Cu(I)-catalyzed dimerization reaction. Subjection of a variety of enantioenriched substituted 2-pyridyl alcohols to a one-pot protocol generates the desired products in good yields and diastereoselectivities and with ee's up to >99%.     

Copper-catalyzed methylation of 1,3-diketones with tert-butyl peroxybenzoate

Copper-catalyzed radical methylation of 1,3-diketones with tert-butyl peroxybenzoate in air is described, providing a general pathway to α-methyl 1,3-diketones in moderate to good yields. This protocol has been scaled up to 50 g, and one of the synthesized products can be used in the synthesis of medicine, Rosuvastatin.     

1-aza-1,3-enynes in synthesis of substituted 4H-[1,3]thiazino[3,2-a]benzimidazol-4-ols

Reaction of N-tert-butyl-1-aza-1,3-enynes with symmetrically substituted 2-mercaptobenzimidazoles in water-alcohol solutions afford 4H-[1,3]thiazino[3,2-a]benzimidazol-4-ols. The structure of compounds obtained was proved by the ¹H and ¹³C NMR spectroscopy and X-ray diffraction data.     

Copper-catalyzed synthesis of purine-fused polycyclics

A novel protocol for a Cu-catalyzed direct C((sp(2)))-H activation/intramolecular amination reaction of 6-anilinopurine nucleosides has been developed. This approach provides a new access to a variety of multiheterocyclic compounds from purine compounds via Cu-catalyzed intramolecular N-H bond tautomerism which are endowed with fluorescence.     

Copper-catalyzed regiospecific synthesis of N-alkylbenzimidazoles

A copper-catalyzed method is described for the preparation of N-alkylbenzimidazoles in regioisomerically pure form starting from o-haloanilines. The method utilizing CuI and trans-N,N'-dimethyl-1,2-cyclohexanediamine allows the preparation of N-alkylbenzimidazoles in good to excellent yields.     

Dialkylaluminum hydride-promoted cyclodimerization of silylated 1,3-enynes via skeletal rearrangement

The dialkylaluminum hydride-promoted reaction of 1-silylalk-3-en-1-ynes gave symmetrical 1,2,3,5-tetrasubstituted benzenes as single regioisomers. The novel cyclodimerization via skeletal rearrangement can be rationalized by an unprecedented mechanism involving sequential hydroalumination, alkene isomerization, carboalumination, carbon-carbon bond cleavage, and retro-hydroalumination.     

Synthesis of bromoallenyl pyrrolidines via 1,4-addition to 1,3-enynes

The discovery of the novel reactivity of conjugated enynes,mediated by readily available halogenation reagents,opens a broad range of mechanistically unique pathways for the synthesis of highly functionalized chiral allene derivatives.Bromoallenyl pyrrolidines can be synthesized via 1,4-addition of sulfonamide nitrogen nucleophiles and halogens to conjugated enynes.This process can lead to simultaneous formation of a highly functionalized axially chiral allene and a stereogenic center under economical and e...     

Copper-catalyzed three-component one-pot synthesis of quinazolines

Two efficient approaches to multi-substituted quinazolines by the three-component one-pot reaction of o-bromo aromatic ketones/aldehydes, ammonia water and aromatic aldehydes, or primary alcohols catalyzed by CuCl have been developed.     

Reactions of benzimidazole-2-thiol with N-alkyl-1-aza-1,3-enynes

Reactions of N-alkyl-1-aza-1,3-enynes with benzimidazole-2-thiol in anhydrous dimethylformamide have been studied. The structure of the obtained compounds has been elucidated from the NMR data.