5-cyano-3,4-dihydroxypyrrolidin-2-ones has been achieved by the use of the commerciallyavailable and inexpensive reagent, molecular iodine, in the presence oftert-butyldimethyl cyanide. Interestingly, the catalyst directs the reaction toward the selective rearrangement reaction of the β-lactam nucleus rather than cyanohydrin formation.
I2-Catalyzed enantioselective ring expansion of β-lactams to γ-lactams through a novel C3–C4 bond cleavage. Direct entry to protected 3,4-dihydroxypyrrolidin-2-one derivatives
Molecular iodine (10 mol%) efficiently catalyzes the ring expansion of 4-oxoazetidine-2-carbaldehydes 1 in the presence of tert-butyldimethyl cyanide to afford protected 5-cyano-3,4-dihydroxypyrrolidin-2-ones 2 with good yield and high diastereoselectivity, through a novel C3âC4 bond cleavage of the β-lactam nucleus.
Ring Expansion versus Cyclization in 4-Oxoazetidine-2- carbaldehydes Catalyzed by Molecular Iodine: Experimental and Theoretical Study in Concert
作者:Benito Alcaide、Pedro Almendros、Gema Cabrero、Ricardo Callejo、M. Pilar Ruiz、Manuel Arnó、Luis R. Domingo
DOI:10.1002/adsc.201000171
日期:——
yield and high diastereoselectivity, through a C3C4 bondcleavage of the β‐lactamnucleus. Interestingly, in contrast to the iodine‐catalyzed reactions of 3‐alkoxy‐β‐lactam aldehydes which lead to the corresponding γ‐lactam derivatives (rearrangement adducts), the reactions of 3‐aryloxy‐β‐lactam aldehydes under similar conditions gave β‐lactam‐fused chromanes (cyclization adducts) as the sole products