Stereoselective reactions of phthalimido-substituted radicalsderivedfrom (±)-threonine with different radical traps are reported (Scheme 3, Table 1). A strong influence of the nature of the radical trap on the stereoselectivity was noticed. Small nucleophilic radical traps gave preferentially the syn products. The observed selectivities are explained with the A1,3 strain model and depend on steric
Acid-mediated intramolecular cationic cyclization using an oxygen atom as internal nucleophile: synthesis of substituted oxazolo-, oxazino- and oxazepinoisoindolinones
12–15 and 19) is described in three steps according to an acidic α-oxoamidoalkylation reaction from ready available phthalic anhydride by successive imidation, sodium borohydridereduction and intramolecular cationic cyclization involving N-acyliminium species. The relative stereochemistry accompanying these reactions was also discussed.