Synthetic Entry to Polyfunctionalized Molecules through the [3+2]-Cycloaddition of Thiocarbonyl Ylides

Here we present a comprehensive study
on the [3+2]-cycloaddition
of thiocarbonyl ylides with a wide variety of alkenes and alkynes.
The obtained dihydro- and tetrahydrothiophene products serve as exceptionally
versatile intermediates providing access to thiophenes, dienes, dendralenes,
and vic-quarternary carbon centers. The use of high-pressure
conditions enables thermally unstable, sterically encumbered or moderately
reactive substrates to undergo the cycloaddition under mild conditions,
thereby increasing the yield by up to 58%. In addition, we showcase
its utility by the formal syntheses of the pharmaceuticals NGB 4420
and tenilapine.