Switching Selectivity of α-Enolic Dithioesters: One Pot Access to Functionalized 1,2- and 1,3-Dithioles

Abstract

An operationally simple cascade protocol has been developed for the construction of 1,2- and 1,3-dithiole derivatives from α-enolic dithioesters. 1,2-Dithioles are achieved by the reaction of dithioesters with elemental sulfur in the presence of InCl under solvent-free conditions. 1,3-Dithioles have been constructed via DABCO mediated self-coupling of dithioesters in open air enabling the formation of two new C-S bonds and one ring in a single operation in contiguous fashion. The reactions proceeded smoothly affording the desired sulfur-rich heterocycles in good to excellent yields, exhibiting gram-scale ability and broad functional group tolerance utilizing easy to handle cheap and easily available reagents. The probable mechanisms for the formation of 1,2- and 1,3-dithioles from α-enolic dithioesters have been suggested.

Site‐Specific S‐Allylation of α‐Enolic Dithioesters with Morita‐Baylis‐Hillman Acetates at Room Temperature: Precursor for Thiopyrans

“… [a] Reactions were performed with 1 mmol of each 1 a and 2 a . [b] Isolated yield. [c] Both the starting materials remained unconsumed. [d] Formation of 1,3‐dithiols (12–20%) was observed at the end of the reaction. [e] Some amount of both the starting materials remained unreacted.…”

“…The above observation was encouraging enough to optimize the reaction conditions to get the higher yield of products 4 a and 5 a . It is worth to mention that in presence of Et 3 N under ethanol reflux, some amount (12–20%) of 1,3‐dithiol has also been produced . Increasing the time of the reaction under ethanol reflux, increased the yield of compound 5 a to 47% and decreased the yield of compound 3 a to 25% (Table , entries 12–14), along with trace amount of compound 4 a .…”

Brønsted acid-catalyzed metal-free one-pot synthesis of benzimidazoles via [4+1] heteroannulation of ortho-phenylenediamines with β-oxodithioesters

“…In continuation of our research interests toward the synthetic utility of β-oxodithioesters, [33][34][35][36][37][38][39][40][41] in order to access diverse structurally challenging heterocycles via one-pot solvent-free synthetic protocols, we report herein an operationally simple and straightforward synthesis of benzimidazoles via one-pot domino reaction involving a sequence of imine formation/N-cyclization/C-C bond cleavage cascade in good to excellent yields (Scheme 1). To the best of our knowledge, there is no report for the synthesis of 2-substituted benzimidazoles directly from β-oxodithioesters under solventless metal-free conditions.…”

Synthesis and Reactivity of 3H-1,2-dithiole-3-thiones

“…Unfortunately, it is still unclear whether this method is applicable to other ketones. 5-Substituted 1,2-dithiole-3-thiones could also be obtained from α-enolic dithioesters [39]. Treatment of α-enolic dithioesters with easy-to-use reagents, namely, elemental sulfur and InCl 3 , at 90 • C under solvent-free conditions in air gave 3H-1,2dithiole-3-thiones in good to excellent yields and showed good functional group tolerance to both electron-donating and electron-withdrawing groups (Scheme 7).…”