Synthesis of carborane-fused cyclobutenes and cyclobutanes

Transmetalation of carborane-fused zirconacycles to Cu（II） induces the C-C coupling reaction to form four-membered rings. This serves as a new efficient and general methodology for the generation of a series of carborane-fused cyclobutenes and cyclobutanes. A reaction mechanism involving transmetalation to Cu（II） and reductive elimination is proposed.

Mukaiyama Aldol Reaction of 1,2-Bis(trimethylsiloxy) Cyclobutene Catalyzed by Magnesium(II) Iodide

Efficient Mukaiyama-type aldol reaction of 1, 2-bis(trimethylsiloxy)cyclobutene with aromatic aldehydes catalyzed by MgI2 is reported. The resulting succinoylation product of aldehyde was converted into the synthetic useful g-lactone and butenolide derivatives.

Organocatalytic asymmetric[2+2] cycloaddition of alkynes with quinones

A chiral phosphoric acid catalyzed enantioselective[2+2] cycloaddition of alkynylindols or alkynylnaphthols with quinones is disclosed.A class of functionalized cyclobutenes with excellent yields,diastereo-and enantioselectivities were prepared under mild reaction conditions(70 examples,up to 99%yield,99%ee,all>50:1 dr).Mechanistic studies revealed that a dearomatization of indole or naphthol occurred to initiate the cycloaddition,followed by an intramolecular Michael addition with in situ generated allene-iminium or vinylidene-quinone methide intermediate.The competitive[2+3] cycloaddition was prevented in this catalytic system.An interesting central to axial chirality conversion via a rearrangement process was realized during transformation of the product.

Catalytic Enantioselective Construction of 6-4 Ring-Junction All-Carbon Stereocenters and Mechanistic Insights

Comprehensive Summary Developing reactions for the synthesis of 6-6-4 and 6-4 carbocyclic scaffolds with a chiral quaternary center at the bridgehead position is highly desired,considering the existence of such skeletons in natural products with biological activities and the potential of using these molecules for downstream studies in chemical biology and medicinal chemistry.Report here is accessing these target skeletons with high chemo-,regio-and enantio-selectivities through Pd(ll)/chiral N,N'-disulfonyl bisimidazoline(Bim)ligand-catalyzed asymmetric reaction of yne-allenones and arylboronic acids.

Visible-Light-Mediated Synthesis of Cyclobutene-Fused Indolizidines and Related Structural Analogs

Expedient assembly of unprecedented molecular scaffolds from readily accessible starting materials in a sustainable fashion is highly pursued in modern organic chemistry.Herein,the first catalytic intramolecular dearomative[2+2]cycloaddition of indoles or pyrroles with alkynes is achieved via visible-lightmediated energy-transfer catalysis.This method enables the synthesis of cyclobutene-fused indolizidines,which are otherwise challenging to access,in high yields with exclusive selectivity.The reaction profiles are well documented by density functional theory(DFT)calculations.In addition,this protocol can be extended to the synthesis of cyclobutane-fused indolizidines and related structural analogs.Diverse elaborations of the products are achieved.

Palladium-catalyzed cyclobutenation of aryl chlorides with norbornenes

A palladium-catalyzed cyclobutenation of readily available aryl chlorides and norbornene derivatives is reported here.Under the optimum reaction conditions,various valuable benzocyclobutene derivatives were prepared efficiently via Heck-Catellani reaction.The key is the employment of bulky t-Bu_(3)PHBF_(4) phosphine ligand which promoted C-C reductive elimination from the palladacycle.