Light-Driven Intramolecular Cyclopropanation of Alkene-Tethered N-Tosylhydrazones: Synthesis of Fused-Cyclopropane γ-Lactones.

Fused-cyclopropane ring-containing γ-lactone compounds are versatile building blocks in many fields, including the synthesis of biologically active compounds. Here, we report the light-driven intramolecular cyclopropanation of alkene-tethered N-tosylhydrazones in the presence of Cs2CO3 and visible light. We have synthesized various electronically and sterically substituted and heterocyclic-containing fused-(spiro)cyclopropane γ-lactone compounds in good yields under transition metal-free conditions using a radical-free approach. In addition, the one-pot synthesis of fused-cyclopropane γ-lactones from α-ketoesters and their synthetic utility are also presented.

Visible-Light-Induced Siloxycarbene Addition to N═N of Azodicarboxylates: Synthesis of Acyl Hydrazides from Acylsilanes.

We report the synthesis of acyl hydrazides from acylsilanes in the presence of visible light without the aid of additives or transition metals. Acylsilanes underwent [1,2]-Brook rearrangement to generate the nucleophilic siloxycarbenes which on further addition to N═N of azodicarboxylates produced the acyl hydrazides. Control experiments indicate that the reaction proceeds through the singlet carbene intermediate. Transformation of the acyl hydrazide functionality to other functional groups was demonstrated, including the synthesis of the drug candidate Moclobemide.

Transition metal-catalyzed reactivity of carbenes with boronic acid derivatives for arylation (alkylation) and beyond.

This comprehensive review article discussed the reactivity of carbenes with boronic acid derivatives for the one-pot synthesis of diarylmethanes, difluoromethylated arenes, aryl and alkyl boron compounds, arylacetic acid derivatives, furan derivatives, and many other compounds. We have summarized the arylation, vinylation, and alkylation of carbenes utilizing various transition metals, viz. palladium, rhodium, copper, and platinum, for the construction of carbon-carbon bonds, carbon-boron bonds, and beyond through the cross-coupling strategy. The reason for the increasing popularity of these novel methodologies is their application in the synthesis and late-stage functionalization of biologically active compounds and natural products. Notably, organoboron compounds are exemplified as versatile synthetic intermediates for constructing various bonds.