Chromium-catalyzed cyclopropanation of alkenes with bromoform in the presence of 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-dihydropyrazine

• Published in: Chemical science (Cambridge) Vol. 11; no. 14; pp. 364 - 369
• Main Authors: Ikeda, Hideaki, Nishi, Kohei, Tsurugi, Hayato, Mashima, Kazushi
• Format: Journal Article
• Language: English
• Published: CAMBRIDGE Royal Soc Chemistry 11.03.2020; Royal Society of Chemistry; The Royal Society of Chemistry
• Subjects: Alkenes; Chemistry; Chemistry, Multidisciplinary; Crystallography; Esters; Ethers; Physical Sciences; Science & Technology; Substrates; Trivalent chromium; DIPHENYLDIAZOMETHANE; STEREOSELECTIVE CYCLOPROPANATION; REAGENTS; ENANTIOSELECTIVE SYNTHESIS; ALKYL; ALLYLIC ALCOHOLS; ASYMMETRIC CYCLOPROPANATION; DECOMPOSITION; SILYLCYCLOPROPANATION; ELECTRON-DEFICIENT OLEFINS
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d0sc00964d

Chromium-catalyzed cyclopropanation of alkenes with bromoform was achieved to produce the corresponding bromocyclopropanes. In this catalytic cyclopropanation, an organosilicon reductant, 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-dihydropyrazine ( 1a ), was indispensable for reducing CrCl 3 (thf) 3 to CrCl 2 (thf) 3 , as well as for in situ generation of (bromomethylidene)chromium( iii ) species from (dibromomethyl)chromium( iii ) species. The (bromomethylidene)chromium( iii ) species are proposed to react spontaneously with alkenes to give the corresponding bromocyclopropanes. This catalytic cyclopropanation was applied to various olefinic substrates, such as allyl ethers, allyl esters, terminal alkenes, and cyclic alkenes. Chromium-catalyzed cyclopropanation of alkenes with bromoform was achieved to produce the corresponding bromocyclopropanes.