The Reactions of Hydrazines with α-Lactams. Regiochemistry of Hydrazine Addition and Subsequent Ring Closure to N-Aminohydantoins or 1,2,4-Triazine-3,6-diones
Origins of Regioselectivity in the Reactions of .alpha.-Lactams with Nucleophiles
摘要:
Regioselectivity in the reaction of alpha-lactams with nucleophiles results from two competing steps. Nucleophilic addition to the carbonyl group of the alpha-lactam, which yields rearranged, acyl-substituted products, is dependent on the nucleophilicity and the concentration of the nucleophile. Ring opening of the alpha-lactam to an ion pair intermediate, which gives nucleophile incorporation at C-2, is dependent on electronic effects of substituents at C-2. Groups which can stabilize positive charge at C-2 speed up ion pair formation, whereas electron-withdrawing groups slow the ring opening and give more carbonyl addition product. These factors are used to control the regioselectivity and produce a series of unsymmetric urea peptide mimetics in high yields and with complete regiochemical control.
Reaction of Hydrazines with .alpha.-Lactams for the Preparation of 1,2,4-Triazine-3,6-diones and Aza-Urea Peptide Mimetics
作者:Robert V. Hoffman、Naresh K. Nayyar
DOI:10.1021/jo00123a048
日期:1995.9
Improved Methodology for the Generation and Trapping of α-Lactams by Weak Nucleophiles
作者:Robert V. Hoffman、Madhava M. Reddy、Francisco Cervantes-Lee
DOI:10.1021/jo991732g
日期:2000.4.1
The Reactions of Hydrazines with α-Lactams. Regiochemistry of Hydrazine Addition and Subsequent Ring Closure to <i>N</i>-Aminohydantoins or 1,2,4-Triazine-3,6-diones
作者:Robert V. Hoffman、Madhava M. Reddy、Curtis M. Klumas、Francisco Cervantes-Lee
DOI:10.1021/jo981650c
日期:1998.11.1
Origins of Regioselectivity in the Reactions of .alpha.-Lactams with Nucleophiles
作者:Robert V. Hoffman、Naresh K. Nayyar、Wenting Chen
DOI:10.1021/jo00118a032
日期:1995.6
Regioselectivity in the reaction of alpha-lactams with nucleophiles results from two competing steps. Nucleophilic addition to the carbonyl group of the alpha-lactam, which yields rearranged, acyl-substituted products, is dependent on the nucleophilicity and the concentration of the nucleophile. Ring opening of the alpha-lactam to an ion pair intermediate, which gives nucleophile incorporation at C-2, is dependent on electronic effects of substituents at C-2. Groups which can stabilize positive charge at C-2 speed up ion pair formation, whereas electron-withdrawing groups slow the ring opening and give more carbonyl addition product. These factors are used to control the regioselectivity and produce a series of unsymmetric urea peptide mimetics in high yields and with complete regiochemical control.