Benzoic Acid Catalyzed Annulations of α-Amino Acids and Aromatic Aldehydes Containing an ortho-Michael Acceptor: Access to 2,5-Dihydro-1H-benzo[c]azepines and 10,11-Dihydro-5H-benzo[e]pyrrolo[1,2-a]azepines

Abstract

A novel one-pot efficient synthesis of 2,5-dihydro-1H-benzo[c]azepines and 10,11-dihydro-5H-benzo[e]pyrrolo[1,2-a]azepines from α-amino acids and aromatic aldehydes containing an ortho-Michael acceptor is reported via decarboxylative annulations without metal catalysts in yields of 52-91%. Under microwave irradiation, this protocol provides rapid access to polycyclic ring systems (only 5 min in most cases).

An Ugi Reaction Incorporating a Redox-Neutral Amine C–H Functionalization Step

“…Mechanistically distinct from the reactions outlined in eqs –3, a decarboxylative version of the Ugi reaction was recently reported that employs proline as the starting material (eq 4). , Here, we report a new type of Ugi variant that enables the α-amidation of cyclic amines via redox-neutral α-C–H bond functionalization (eq 5). , …”

Recent Advances on Diverse Decarboxylative Reactions of Amino Acids

“…Yu's group described a one‐pot metal‐free synthesis of 2,5‐dihydro‐1 H ‐benzo[ c ]azepine derivatives 234 from α‐amino acids 232 and aromatic aldehydes 233 containing an ortho ‐Michael acceptor via decarboxylative annulation under microwave irradiation (Scheme ) . Here, first the condensation of aromatic aldehyde 235 with l ‐proline 205 provided the oxazolidinone 236 which underwent decarboxylation to produce the azomethine ylide.…”

Recent Advances on Amino Acid Modifications via C–H Functionalization and Decarboxylative Functionalization Strategies

“…The protocol leads to the synthesis of 2,5‐dihydro‐1 H ‐benzo[ c ]azepines 197 and 10,11‐dihydro‐5 H ‐benzo[ e ]pyrrolo[1,2‐ a ]azepines 198 in moderate to excellent yields. Under microwave irradiation conditions the protocol provides a rapid synthesis of polycyclic systems (Scheme ) …”