A new general synthesis of diastereomerically pure Boc-protected 1-alkenyl 2-aminoalkyl sulfoxides has been developed (Soderman and Schwan, J. Org. Chem. 2013 , 78, 1638). The protocol employs 1-alkenesulfenate anions, which possess the general structure RCH=CHSO-M+ as nucleophiles to deliver a sulfur and an oxygen to a chiral electrophilic iodide in a doubly diastereoselective manner. The free amine (or ammonium TFA) form of the (RS,SC or SS,RC)-1-alkenyl 2-aminoalkyl sulfoxides undergo a stereoselective cyclization to create trans-3,5-disubstituted thiomorpholine S-oxides, a process that introduces a third stereogenic centre. Alternatively, conversion of the sulfoxides to the sulfones creates enantiomerically pure 1-alkenyl 2-aminoalkyl sulfones, which by contrast, undergo cyclization to give the complementary cis-3,5-disubstituted thiomorpholine S,S-dioxides. Selected versions of these heterocycles are advanced further to offer a new and enantioselective preparation of cis- and trans-2,5-disubstituted pyrrolidine alkaloids, known constituents of ant venoms.

Stereodivergent pathways characterize the aza-Michael cyclization of selected �-aminoalkyl 1-alkenyl sulfoxides and sulfones

248th National Meeting (2014)

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