Construction of remote cyano-substituted quaternary carbon centers via nickel-catalyzed migratory hydrocyanation of unconjugated dienes

The transition-metal-catalyzed migratory functionalization has emerged as a robust protocol for the building of C–C bonds remote from the“initiation”position.However,a similar strategy for the construction of quaternary carbon centers is still underdeveloped and only a limited number of reports exist.Herein,we report a nickel-catalyzed migratory hydrocyanation of unconjugated dienes to construct remote cyano-substituted quaternary carbon centers.This transformation features exceptional regioselectivity,mild reaction conditions,broad substrate scope and high yields.The synthetic utility of this method has been highlighted by a series of product derivatizations,and the potential of this transformation has been extended to synthesize TRPV1 antagonist and the key intermediate in the total synthesis of quebrachamine.Density functional theory(DFT)studies unveiled that the specific catalytic pocket assumed a significant role in the selective formation of cyano-substituted quaternary carbon centers.

Construction of highly congested quaternary carbon centers by NHC catalysis through dearomatization

A NHC-catalyzed hypervalent iodine reagents and transition-metal free redox-neutral dearomatization of phenols is reported.This protocol provides an efficient access for highly congested quaternatry carbon centers construction.It also features operationally simplicity,mild reaction conditions and good functional group tolerance.Moreover,the reported procedure can be easily emplified to 1 g scale.Mechanism study reveals the dearomative transformation possibly undergoes a single electron transfer process with NHC radical cation as a reactive intermediate.

Brønsted acid-catalyzed 1,6-hydrophosphination of propargylic para-quinone methides and aza-para-quinone methides for the rapid construction of phosphorus-substituted quaternary carbon centers

An intriguing Brønsted acid-catalyzed 1,6-hydrophosphination of in situ generated propargylic para-quinone methides(p-QMs)and aza-para-quinone methides(aza-p-QMs)with H-phosphorus oxides via dehydration/1,6-addition under ultrasonic irradiation is described.This methodology provides a rapid and green approach for the construction of diarylmethyl phosphorus oxides bearing phosphorus-substituted quaternary carbon centers in high yields(up to 98%yield)within merely 5min.This environmentally benign protocol represents a unique example of 1,6-conjugate additions of propargylic p-QMs and aza-p-QMs for site-selective C-P bond formation in an operationally simple and atom-economical manner.The use of readily available Brønsted acid catalyst,operationally simplicity,high yields,and high atom economy make this protocol very facile,practical,easily scaled-up and environmentally friendly.

I_(2)-DMSO-Mediated Multicomponent [2+1+1+1] Annulation Reaction via Ethyl Nitroacetate C-NO_(2), Bond Cleavage as a C1 Synthon: A Route to Multisubstituted β-Pyrrolidinones Derivatives with a Quaternary Center

A[2+1+1+1]cyclization reaction has been developed for the synthesis of multisubstituted 6-pyrrolidinones from commercially available aryl methyl ketones,primary amines,and ethyl nitroacetate.In this I_(2)-DMSO-meditated process,the C-NO_(2) bond of ethyl nitroacetate is cleaved,affording a C1 synthon,and the formation of two C-C and two C-N bonds and a quaternary carbon center are constructed in one pot.This method has good substrate compatibility and permits the late-stage modification of pharmaceutical compounds.

Organophosphine bearing multiple hydrogen-bond donors for asymmetric Michael addition reaction of 1-oxoindane-2-carboxylic acid ester via dual-reagent catalysis

Multiple hydrogen bonds containing nucleophilic phosphines derived from dipeptide dual-reagents catalyzed asymmetric Michael addition reactions between indene esters and activated olefins in high yields and good to excellent enantioselectivities under mild reaction conditions.The success of current highly selective reactions should provide inspiration for expansion to other reactions and would open up new paradigms for the synthesis of indanone derivatives bearing chiral quaternary carbon centers.

Michael Addition Reaction of Fluorinated Nitro Compounds

The Michael addition reactions of fluorinated nitro compounds with electron deficient olefins to give γ-fiuoro-γ-nitro-esters, nitriles and ketones which bear a fluorinated quaternary carbon center were reported. The reactions were promoted by TMG, affording the desired adducts in acceptable to good yields.