Passerini (P-3CR) and Passerini-Smiles reactions were investigated in azetidine-2,3-diones, affording the corresponding 3,3-disubstituted-beta-lactams with complete diastereoselectivity in high yields. The study has been carried out using different isocyanides, carboxylic acids, and phenols showing the scope of both reactions. In addition, the regioselective synthesis of highly functionalized beta-lactam-triazole hybrids has been developed via a Passerini/CuAAC sequence. Interestingly, the use of dialkynes/diazides or trialkynes/triazides as linkers in the CuAAC step has allowed the synthesis of C-2 and C-3 symmetric beta-lactam-triazole hybrids, respectively.
Organocatalyzed Three-Component Ugi and Passerini Reactions of 4-Oxoazetidine-2-carbaldehydes and Azetidine-2,3-diones. Application to the Synthesis of γ-Lactams and γ-Lactones
P-3CR adducts have been obtained in good yields and reasonable diastereoselectivities. Phenyl phosphinic acid has been the catalyst of choice to study the scope of both organocatalyzed multicomponent reactions using a variety of β-lactams, isocyanides, and amines. Highly functionalized U-3CR and P-3CR adducts derived from β-lactams have proved to be useful substrates for the preparation of enantiopure γ-lactams