Continuous-Flow Synthesis of Arylthio-Cyclopropyl Carbonyl Compounds

The straightforward, continuous-flow synthesis of cyclopropyl carbaldehydes and ketones has been developed starting from 2-hydroxycyclobutanones and aryl thiols. This acid-catalyzed mediated procedure allows access to the multigram and easily scalable synthesis of cyclopropyl adducts under mild conditions, using reusable Amberlyst-35 as a catalyst. The resins, suitably ground and used for filling steel columns, have been characterized via TGA, ATR, SEM and BET analyses to describe the physical-chemical properties of the packed bed and the continuous-flow system in detail. To highlight the synthetic versatility of the arylthiocyclopropyl carbonyl compounds, a series of selective oxidation reactions have been performed to access sulfoxide and sulfone carbaldehyde cyclopropanes, oxiranes and carboxylic acid derivatives.

α,β-Unsaturated Carbonyls for One-Pot Transition-Metal-Free Access to 3,6-Dihydro-2H-pyrans

An efficient protocol has been developed for accessing mono-, di-, and trisubstituted 3,6-dihydro-2H-pyran derivatives by simply subjecting α,β-unsaturated carbonyls to the carefully optimized Corey-Chaykovsky reaction conditions. The strategy provides selectively substituted dihydropyran derivatives in good to excellent yields with a broad substrate scope under very mild reaction conditions. Easy transformation of the final 3,6-dihydro-2H-pyran to the valued 5,6-dihydro-2H-pyran-2-one and tetrahydro-2H-pyran derivatives expanded the scope of this methodology to diverse oxacycles. Further, the developed strategy also found application in a two-step route to racemic goniothalamin, which is widely studied for its cytotoxic behavior.

Visible-light-promoted hydroxysulfonylation of alkylidenecyclopropanes: synthesis of cyclopropane-containing β-hydroxysulfones

Cyclopropane-containing β-hydroxysulfones and cyclopropyl styrenes have been synthesised from readily available ACPs and sulfuryl chloride via visible-light photoredox catalysis.

Acid-catalyzed synthesis of functionalized arylthio cyclopropane carbaldehydes and ketones

A general strategy for the synthesis of arylthio cyclopropyl carbaldehydes and ketones via acid catalysed arylthiol addition/ring contraction reaction sequence has been exploited. The procedure led to a wide panel of cyclopropyl carbonyl compounds in high yields and broad substrate scope.