Synthesis of strained tricyclic beta-lactams by intramolecular [2+2] cycloaddition reactions of 2-azetidinone-tethered enallenols: control of regioselectivity by selective alkene substitution.
A convenient metal-free methodology for the preparation of structurally novel, strained tricyclic beta-lactams containing a cyclobutane ring has been developed. The first examples accounting for the intramolecular [2+2] cycloaddition reactions in beta-lactams have been achieved by the thermolysis of 2-azetidinone-tethered enallenols, which have been prepared in aqueous media by regio- and diastereoselective indium-mediated carbonyl allenylation of 4-oxoazetidine-2-carbaldehydes. Notably, the regioselectivity of the cycloaddition can be tuned in the allene component just by a subtle variation in the substitution pattern of the alkene component.
Alcaide
Benito
B
Departamento de Química Orgánica I, Facultad de Química, Universidad Complutense de Madrid, 28040 Madrid, Spain. alcaideb@quim.ucm.es
Almendros
Pedro
P
Aragoncillo
Cristina
C
Redondo
María C
MC
Torres
M Rosario
MR
D000475:Alkenes / Q000737:chemistry*; D001384:Azetidines / Q000737:chemistry*; D003503:Cyclobutanes / Q000737:chemistry*; D009281:Naphthalenes / Q000737:chemistry; D047090:beta-Lactams / Q000138:chemical synthesis*
C116379:2-azetidinone; D000475:Alkenes; D001384:Azetidines; D003503:Cyclobutanes; D009281:Naphthalenes; D047090:beta-Lactams; C110055:allenolic acid