4-Alkenyl-5H-1,2,3-oxathiazole 2,2-dioxides in catalytic and enantioselective [4 + 2] cycloaddition through iminium activation. Straightforward access to the trans-decaline framework and to densely functionalized cyclohexanes

Abstract

4-Alkenyl-5H-1,2,3-oxathiazole 2,2-dioxides undergo Michael/Michael cascade reaction with enals through iminium/enamine activation.

The Pd-catalysed asymmetric allylic alkylation reactions of sulfamidate imines

“…1a ). The only reports of such reactions are from the groups of Vicario and Samanta, who have both demonstrated organocatalyzed diastereo- and/or enantio-selective reactions of sulfamidate imines to provide stereodefined scaffolds, such as spiro sulfamidate imine-fused δ-lactone B , 27 sulfamidate imine-fused cyclohexanes and trans -decalins C , 28,29 and 3,3-disubstituted oxindoles D . 30 None of these reactions involve reaction of a 5-substituted cyclic imine to directly form a tetra-substituted stereogenic centre in the product.…”

Organocatalytic Transannular Approach to Stereodefined Bicyclo[3.1.0]hexanes

“…In this sense, we recently reported the catalytic and enantioselective synthesis of highly functionalized oxathiazole-2,2-dioxide-fused cyclohexane scaffolds ( 3 ) through Michael/Michael cascade reaction between enals ( 2 ) and 4-alkenyl sulfamidate imines ( 1 ) in the presence of a chiral secondary amine catalyst (see Scheme ). These highly functionalized cyclohexanes incorporate a potentially nucleophilic site at the formyl-containing carbon atom, together with an electrophilic site by means of the good leaving-group ability of the sulfonate group, and both reactive points are located at a strategic 1,3-relative position. This made us envision the potential of these substrates as starting materials for the construction of highly functionalized bicyclo[3.1.0]­hexanes ( 4 ) via transannular reaction, also being able to obtain these adducts as single stereoisomers provided that the key transannular reaction proceeds in a diastereoselective manner under efficient substrate control.…”

“…This epimerization process can take place either at the final product or at the corresponding oxathiazole precursor during the hydrolysis. With the best conditions in hands, we proceeded to extend the reaction to other substrates 3 (Table ), which were synthesized in an enantioenriched fashion through our previously reported methodology . As shown in Table , when a variety of starting products incorporating a methyl group at R 1 and aryl groups with different substitution patterns at the R 2 position were tested, the reaction proceeded with high yield and diastereoselectivity (entries 1–8), observing that the reaction provided only inferior yields and a somewhat lower degree of diastereoselectivity when a phenyl substituent was placed at R 1 (entry 9).…”