A novel application of 2-silylated 1,3-dithiolanes for the synthesis of aryl/hetaryl-substituted ethenes and dibenzofulvenes

作者：Mloston Grzegorz; Pipiak Paulina; Hamera Faldyga Roza; Heimgartner Heinz

来源：Beilstein Journal of Organic Chemistry, 2017, 13: 1900-1906.

DOI：10.3762/bjoc.13.185

• diazomethanes
• 1,3-dipolar cycloadditions
• olefination reactions
• reaction mechanisms
• thioketones

Trimethylsilyldiazomethane (TMS-CHN2) reacts readily with hetaryl thioketones to give sterically crowded 2-trimethylsilyl4,4,5,5- tetrahetaryl-1,3-dithiolanes with complete regioselectivity at -75 degrees C as well as at rt. Thiofluorenone, a relatively stable and highly reactive aryl thioketone, yields upon treatment with TMS-CHN2 at -60 degrees C the corresponding 1,3,4-thiadiazoline. This unstable cycloadduct undergoes decomposition at ca. -45 degrees C and the silylated thiocarbonyl S-methanide generated thereby is trapped with complete regioselectivity by aryl or hetaryl thioketones forming also sterically crowded 2-trimethylsilyl-1,3dithiolanes. The obtained 1,3-dithiolanes, by treatment with an equimolar amount of TBAF in a one-pot procedure, are converted in high yields into hetaryl/aryl-substituted ethenes or dibenzofulvenes, respectively, via a cycloreversion reaction of the intermediate 1,3-dithiolane carbanion. The presented protocol offers a new, highly efficient approach to tetrasubstituted ethenes and dibenzofulvenes bearing aryl and/or hetaryl substituents.

• 出版日期2017-9-8