Chemoselective Synthesis of Unsymmetrical Dithioacetals through Sequential Carbene Insertion and Acetal Exchange of Acylsilanes and Thiols under Visible Light Irradiation

Abstract

Dithioacetals are a frequently used motif in synthetic organic chemistry, and most existing reports discuss only symmetrical dithioacetals. Examples of unsymmetrical dithioacetals are scarce, and few general methods for the selective synthesis of these compounds exists. An intriguing visible-lightinduced strategy has been established in this work for sequential reactions of S−H insertion and acetal exchange between acylsilanes and two different thiols that deliver a wide variety of unsymmetrical dithioacetals in moderate yields. The unsymmetrical dithioacetals were obtained with high selectivity, and a great variety of functional groups were tolerated.

Photoinduced Asymmetric Formal Siloxycarbene Insertion into sp3 C–H Bonds Enabled by Chiral Phosphoric Acid

“…Among the reactions in which siloxycarbenes participate, researchers keep a close watch on carbene insertion reactions into the X–H bond because they provide a rapid and effective way to construct the C–X bond (X = carbon, heteroatoms). Currently, there are some reports about the singlet siloxycarbene insertion into a (hetero) X–H bond, such as O–H, S–H, B–H, N–H, P–H, etc. − However, very few examples of siloxycarbene insertion into the C–H bond have been reported (Scheme ). Dong and co-workers reported intramolecular benzylic C–H functionalization with acylsilane substitutes.…”

“…They are a kind of highly reactive intermediate and usually own nucleophilic reactivity in various reactions, for example, carbene insertion reaction into X–H bonds (X = O, N, B, C, etc.) in their singlet state, − cyclization reactions with alkenes and alkynes, and nucleophilic addition to electrophiles such as carbonyl compounds . A series of organosilicon derivatives could be obtained starting with siloxycarbenes.…”