Annulative Aminosulfonylation of Unactivated Alkenes for Accessing Pyrazolines via Multicomponent SO2 Insertion.

A direct arylsulfonylation of ß,γ-unsaturated hydrazones method, in which sulfonated pyrazolines are accessed by a three-component reaction of ß,γ-unsaturated hydrazones, DABSO, and aryldiazonium tetrafluoroborates, has been developed without external oxidants or catalysts. This transformation is triggered by the formation of arylsulfonyl radicals in situ from the reaction of aryldiazonium tetrafluoroborates and DABSO, and is enabled by controllable generation of C center radical, in which DABSO was utilized as the sulfone source and an oxidant in this radical-mediated cascaded reaction. A wide range of substrates can be applied in this process to afford pyrazolines in good yield, and it is amenable for gram-scale synthesis.

Visible-light-catalyzed synthesis of 1,3-benzoxazines via formal [4 + 2] cycloaddition of oximes with o-hydroxybenzyl alcohols.

A formal [4 + 2] cycloaddition of oximes with o-hydroxybenzyl alcohols was developed to easily synthesize diverse 1,3-benzoxazine derivatives. This synthesis was achieved under visible light-based organocatalytic and TsOH conditions. The reaction proceeds through the photoisomerization of oximes via visible light-mediated energy transfer, followed by the nucleophilic attack of o-QMs to oximes as a 1,2-dipole synthon, cyclization, and isomerization. The reaction exhibits a broad substrate scope and can be carried out under mild conditions. To demonstrate its synthetic usefulness, a gram-scale reaction was conducted, and the resulting 1,3-benzoxazine products were further transformed into other valuable compounds.