The syn-Selective Conjugate Addition of Amines to Enoates Derived from D-Mannitol.

Abstract The syn -selective conjugate addition of neat amines to enoates Z - 1 and E - 1 , prepared from d -(+)-mannitol, is reported. The reactions with benzyl and allylamine 2a , d at −50 °C or 2e at −25 °C in the absence of a solvent led to syn -adducts in moderate to good chemical yields and good syn / anti ratios, and were accelerated in the presence of DBU. Enoate Z - 1 was more reactive than E - 1 , leading to products with better syn -selectivity. The syn -selectivity slightly decreased for reactions at rt. The reaction of both enoates with primary amines 2c , d (Ph changed by 2- and 3-pyridyl) only occurred at rt, leading to adducts in good chemical yields and with moderate to good syn -selectivities. Secondary acyclic amine 2f showed very low reactivity (rt, DBU, several hours) and led to the adduct in moderate chemical yields and with low syn -stereoselectivity while higher reactivity and moderated yields and syn -selectivities were observed for cyclic secondary amines 2g – i .