Behnke NE, Siitonen JH, Chamness SA, Kürti L. Synthesis of Highly Substituted Cyclopropanes via the Quasi-Favorskii Rearrangement of α,α-Dichlorocyclobutanols.
Org Lett 2020;
22:5715-5720. [PMID:
32330043 DOI:
10.1021/acs.orglett.0c01229]
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Abstract
A method for the synthesis of highly substituted cyclopropanes via a quasi-Favorskii rearrangement is described. The method includes the combination two chemical transformations starting from α,α-dichlorocyclobutanones prepared via the [2 + 2] Staudinger ketene cycloaddition between either terminal- or cis-olefins and dichloroketene. First, α,α-dichlorocyclobutanones are reacted with organocerium reagents to afford the corresponding tertiary alcohols in good to excellent yields through a nucleophilic addition reaction that provided exclusively anti-products. Second, upon irreversible deprotonation, the tertiary α,α-dichlorocyclobutanols underwent a ring-contraction reaction (i.e., quasi-Favorskii rearrangement) to form structurally diverse cyclopropanes in moderate to good yields. The syn-stereoselectivity during the quasi-Favorskii rearrangement was evaluated using DFT analysis.
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