Trisubstituted Highly Activated Benzo[d]thiazol-2-yl-sulfone-Containing Olefins as Building Blocks in Organic Synthesis

Abstract

In this paper, we report the formation of highly electrophilic 1,1-deactivated olefins, their use as novel synthetic building blocks, and their transformation to structurally diverse molecular scaffolds. Synthesis of 1,1-deactivated olefins substituted with a BT-sulfonyl group and a carbonyl or nitrile, respectively, consists of unusual Ti­(OPr i )4-mediated Knoevenagel-type condensation and proceed in good to excellent yields. Generated olefins can be further transformed in a highly stereoselective manner and in good yields to various polyfunctionalized heterocycles and acyclic molecular scaffolds. Overall, the obtained structures are accessed in two to four steps starting from the (mostly) commercially available aldehydes. In addition, the presence of the BT-sulfonyl group in prepared structures allows for further chemoselective functionalization/post-synthetic transformations to provide structurally diverse final compounds.

Heteroaryl sulfonamide synthesis: scope and limitations

“…Previous observations and data obtained during our research in the field of benzothiazole-2-yl sulfones and sulfonamides showed that sulfone/sylfonamide-bearing C α carbon in the heterocycle is prone to nucleophilic attack. 24–26 We exploited this behaviour, for example, in amine synthesis; 23 however, it also caused the instability of sulfones and sulfonamides on silica gel. 24,27,28 For those reasons we wondered if the quasi-nonexistence of several classes of heteroaryl sulfonamides in the literature 19 might be caused by their instability.…”