No abstract

A metal- and oxidant-free photoinduced strategy for thioxo sulfur-selective trifluoromethylation of β-ketodithioesters at room temperature is reported. Excellent Z/E-stereoselectivity has been achieved with cheap and viable Langlois’ reagent (CF3SO2Na, sodium triflinate) in the presence of eosin Y, which acts as a hydrogen atom transfer (HAT) catalyst. The reaction proceeds via disulfide intermediate disulfanediylbis­(3-(alkylthio)-1-phenylprop-2-en-1-one) (a dimer of β-ketodithioester) followed by complementing proton-coupled electron transfer-mediated reverse HAT cycle of eosin Y. This operationally simple and efficient protocol allows direct access to triflinated α-oxoketene dithioacetals in good to excellent yields bearing diverse synthetically useful functional groups of different electronic and steric nature.

An efficient protocol for visible-light-mediated synthesis of a specific class of 1,2,4-dithiazolidines from β-ketothioamides is devised employing eosin Y as a photoinitiator at ambient temperature in an open pot. The reaction proceeds via an in situ-generated thiyl radical followed by dimerization/deaminative cyclization cascade, enabling the creation of a dithiazolidine ring through successive formation of S–S and N–C bonds under metal- and additive-free conditions. Remarkably, the benign conditions, sustainability, and quantifying forbearance of wide horizons of functional groups are added characteristics to the strategy. The developed hydrogen-atom-transfer methodology will be helpful in postsynthetic modification via added synthetic handles.

Phosphonium ylides are being reported here as a catalyst for the formation of thiazolidines and 1,3-thiazinanes from β-ketothioamides with dihaloalkanes via [3 + 2] and [3 + 3] annulations under metal-free conditions.