Scheme 11. Latvilla's multicomponent reaction. Reagents and conditions: (1) Sc(OTf)3 (20%), 32a, 33, 34b, 4 Å MS, MeCN, Ar, 2 d, rt, d.r. 70 : 30, 83%, [R1,R2,R3 = H]; (2) Sc(OTf)3 (20%), 32b, 33, 34a, EtOH, d.r. 2 : 3 : 1, 82%, [R1,R2,R3=H]; (3) TFA (O2), MeCN–H2O, 71%; (4) Sc(OTf)3 (20%), 32b, 33, 34a, single stereoisomer, [R1,R2 =OAc; R3 =(R)-CH2OAc]; (5) CAN, MeCN, 58%; (6) Sc(OTf)3 (20%), 32a, 33, 34a, d.r. 2 : 5 : 1, 46%, [R1,R2 = H, R3= (R)-CH2OH].
