IODOCYCLIZATION OF THE (TOLYLSULFONYL)CARBAMATES AND (TRICHLOROACETYL)CARBAMATES OF SECONDARY ALPHA-ALLENIC ALCOHOLS - HIGHLY DIASTEREOSELECTIVE SYNTHESIS OF SYN-1,2-AMINO ALCOHOLS AND TRANS-5-ALKYL-2-OXO-OXAZOLIDINE-4-CARBOXYLIC ACIDS

The iodocyclization of tosyl- and (trichloroacetyl)carbamates 9 and 10, respectively, of secondary alpha-allenic alcohols is described. The cyclofunctionalization reactions are highly diastereoselective, providing trans-5-alkyl-4-(1-iodoethylene)-2-oxazolidinones 11 and 12 as the major diastereomers in ratios of 6.3:1 to > 99: < 1. The mechanism of cyclization involves the initial formation of diiodides resulting from the addition of I2 to the terminal olefin of the allene moiety, followed by a kinetically controlled intramolecular SN2' displacement of iodide. Hydrolysis and acetylation of the N-tosyloxazolidinones 11 provide syn-1,2-amino alcohol derivatives 15. Alternatively, ozonolysis of the vinyl iodides derived from the cyclization of the (trichloroacetyl)carbamates 12 provides a novel, efficient, and highly diastereoselective route to trans-5-alkyl-2-oxazolidinone-4-carboxylic acids 25 and esters 26.