학술논문

Lewis-Acid-Catalyzed Oxa-Michael Addition to Give α-Diazo-β-alkoxy Carbonyls and Tetrahydro-3 H -furo[3,4- c ]pyrazoles.
Document Type
Academic Journal
Author
Peck AM; Department of Chemistry, The Univeristy of Vermont, 82 University Place, Burlington, Vermont 05405, United States.; Brewer M; Department of Chemistry, The Univeristy of Vermont, 82 University Place, Burlington, Vermont 05405, United States.
Source
Publisher: American Chemical Society Country of Publication: United States NLM ID: 100890393 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1523-7052 (Electronic) Linking ISSN: 15237052 NLM ISO Abbreviation: Org Lett Subsets: PubMed not MEDLINE; MEDLINE
Subject
Language
English
Abstract
The conjugate addition of alcohols to vinyl diazonium ions formed via Zn(OTf) 2 -catalysis gives α-diazo-β-alkoxy carbonyls. The diazo group is retained in this reaction, and this process is an efficient way to couple a reactive partner to the diazo fragment. As an example, we disclose that addition of allyl alcohols provides tetrahydro-3 H -furo[3,4- c ]pyrazoles via an addition/cycloaddition sequence. This two-step sequence provides good yields and good diastereoselectivity of these sterically hindered pyrazoline scaffolds with up to three quaternary centers and four stereogenic centers. These products can be elaborated to cyclopropane-fused tetrahydrofurans upon liberation of nitrogen. The reaction conditions are mild, operationally simple, and avoid the use of expensive transition metal catalysts.