1,3-dipolar cycloadditions of trimethylsilyldiazomethane revisited: steric demand of the dipolarophile and the influence on product distribution.
The 1,3-dipolar cycloaddition of trimethylsilyldiazomethane with alpha,beta-unsaturated esters was examined. The resulting 1-pyrazolines isomerize to regioisomeric 2-pyrazolines (a or b) or undergo desilylation (c). Acrylates yield only b or c. beta-Substituted dipolarophiles may yield all three types of products. This work demonstrates that the distribution of 2-pyrazoline products is highly dependent on the relative configuration of the substituents on the 1-pyrazoline intermediate.
Simovic
Dragan
D
Department of Chemistry, Florida International University, Miami, Florida 33199, USA.
Di
Mingping
M
Marks
Vered
V
Chatfield
David C
DC
Rein
Kathleen S
KS
D003500:Cyclization; D003978:Diazomethane / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D004952:Esters / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism; D014297:Trimethylsilyl Compounds / Q000138:chemical synthesis / Q000737:chemistry*
D004952:Esters; D014297:Trimethylsilyl Compounds; D003978:Diazomethane; C060070:trimethylsilyldiazomethane