Tetrasilane Used for Divergent Synthesis of Silacycles

Tetrasilane Used for Divergent Synthesis of Silacycles

Author: ChemistryViews

Silacycles can be useful intermediates in organic synthesis and also have uses, e.g., in pharmaceutical and materials chemistry. The synthesis of silacycles can be achieved, for example, by the transition-metal-catalyzed construction of C–Si bonds in annulation or ring-expansion reactions. However, annulations that involve forming two C–Si bonds between a silicon reagent and an organic substrate are less well studied due to a lack of suitable silicon reagents and limited substrate scopes.

Yun Liang, Yuan Yang, Hunan Normal University, Changsha, China, and colleagues have used octamethyl-1,4-dioxacyclohexasilane (ODCS, pictured), which can be easily prepared from 1,2-dichlorotetramethyldisilane, as a reagent for the divergent synthesis of silacycles via a time-controlled, palladium-catalyzed reaction (example product structures pictured). The team reacted acrylamide derivatives with ODCS in the presence of Pd(OAc)2 and PPh3, using K2CO3 as a base and dimethylacetamide (DMA) as the solvent. The reactions were performed at 100 °C.

The team found that controlling the reaction times enabled the divergent synthesis of silacycles with different ring sizes, including ten-membered rings in benzodioxatetrasilecines, seven-membered rings in benzooxadisilepines, and five-membered rings in benzosiloles. Longer reaction times gave smaller rings. The approach can also be used for the synthesis of ten-, seven-, and five-membered fused silacycles from 2-halo-N-methacryloylbenzamides. The researchers investigated the reaction mechanism and found that the seven- and five-membered silacycles are formed via sequential ring contractions of the ten-membered silacycles.


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