1,3-Dipolar Cycloadditions of Trimethylsilyldiazomethane Revisited:  Steric Demand of the Dipolarophile and the Influence on Product Distribution

• Published in: Journal of organic chemistry Vol. 72; no. 2; pp. 650 - 653
• Main Authors: Simovic, Dragan, Di, Mingping, Marks, Vered, Chatfield, David C, Rein, Kathleen S
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 19.01.2007; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Organic; Cyclization; Diazomethane - analogs & derivatives; Diazomethane - chemical synthesis; Diazomethane - chemistry; Esters - chemistry; Exact sciences and technology; Heterocyclic compounds; Heterocyclic compounds with several n hetero atoms in the same ring, in separated rings or in fused rings; Molecular Structure; Organic chemistry; Physical Sciences; Preparations and properties; Science & Technology; Stereoisomerism; Trimethylsilyl Compounds - chemical synthesis; Trimethylsilyl Compounds - chemistry; ENANTIOSELECTIVE SYNTHESIS; DERIVATIVES; ACID; Acrylic acid ester; Unsaturated compound; 1,3-Dipolar cycloaddition; Ester; Steric effect; Nitrogen heterocycle; Relative configuration; Isomerization; Pyrazole derivatives; Dipolarophile; Desilylation
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo061838t

The 1,3-dipolar cycloaddition of trimethylsilyldiazomethane with α,β-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. β-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.