Semipinacol Rearrangement Induced by Cleavage of Dibromocyclopropane

• Published in: European journal of organic chemistry Vol. 2020; no. 27; pp. 4108 - 4111
• Main Authors: Kurimoto, Michitaka, Nakajima, Daisuke, Nishiyama, Yoshitake, Yokoshima, Satoshi
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 23.07.2020; Wiley Subscription Services, Inc
• Subjects: Carbonyl compounds; Carbonyls; Chemical synthesis; Chemistry; Chemistry, Organic; Cleavage; Cyclopropane; Cyclopropanes; Electrocyclic ring opening; Functional groups; Physical Sciences; Quaternary carbon; Rearrangement; Science & Technology; Small ring systems; ENANTIOSELECTIVE SYNTHESIS; STRATEGY; RESOLUTION; Cyclopropanes; RING EXPANSION REACTIONS; REACTIVITY; ALPHA; GEM-DIBROMOCYCLOPROPANES; Electrocyclic ring opening; Quaternary carbon; Small ring systems; FACILE SYNTHESIS; CONSTRUCTION; ASYMMETRIC TOTAL-SYNTHESIS; Rearrangement
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.202000355

A novel semipinacol rearrangement using dibromocyclopropanes as sources of carbocations was developed. Heating dibromocyclopropanes bearing a 1‐hydroxyalkyl group with silver perchlorate and 2,6‐lutidine induced cleavage of the cyclopropane ring to form allyl cations, which underwent 1,2‐shift of a substituent at the α‐position of the hydroxy group to give β,γ‐unsaturated carbonyl compounds having a quaternary carbon at the α‐position. Because the products have convertible functional groups such as bromo, vinyl, and formyl groups, the method is expected to be applicable to the synthesis of various molecules. A novel semipinacol rearrangement using dibromocyclopropanes as sources of carbocations was developed. Heating dibromocyclopropanes bearing a 1‐hydroxyalkyl group with silver perchlorate and 2,6‐lutidine induced cleavage of the cyclopropane ring to form allyl cations, which underwent 1,2‐shift of a substituent at the α‐position of the hydroxy group to give β,γ‐unsaturated carbonyl compounds having a quaternary carbon at the α‐position.