Scheme 1.
Synthesis of benzopyran analogues Aa
R1 = 3,4-dimethoxyphenyl (2a, 3a), 2-pyridinyl (2b, 3b), 2,4-dimethylphenyl (2c, 3c), 4-carboxyphenyl (2d), 2-bromophenyl (2e), 2-fluorophenyl (2f)
aReagents and Conditions: (a) R1NH2, ZnCl2, NaCNBH3, r.t., 11 – 70%; (b) MeI, NaH, THF, r.t., 50 – 81%.Class 2: Benzopyran analogues B