Halocyclopropanes

Halocyclopropanations are found in Section 74F (Alkyls from Alkenes). 

Bromo- and iodocyclopropanes cannot be prepared by the direct halogenation of cyclopropanes. Substituted chloro- and bromocyclopropanes have been synthesized by the photochemical decomposition of a-halodiazomethanes in the presence of olefins iodocyclopropanes have been prepared from the reaction of an olefin, iodoform and potassium f-butoxide followed by the reduction of diiodocyclopropane formed with tri-w-butyl tin hydride. The method described employs a readily available light source and common laboratory equipment, and is relatively safe to carry out. The method is adaptable for the preparation of bromo- and chlorocyclopropanes as well by using bromodiiodomethane or chlorodiiodomethane instead of iodoform. If the olefin used will give two isomeric halocyclopropanes, the isomers are usually separable by chromatography. ... 

Halocyclopropanes, reactions of, 13, 2 Halogen-metal interconversion reactions,... 

Both phase-transfer and crown ether catalysis have been used to promote a-elimination reactions of chloroform and other haloalkanes.90 The carbene is trapped by alkenes to form halocyclopropanes. 

Halocyclopropanes 96 112. According to Clark and coworkers,33 F acts predominantly... 

Lithium-Halogen Exchange and the Chemistry of 1-Lithio-l -halocyclopropanes 1007... 

The formation of allyl cations from halocyclopropanes via ring opening of the unstable cyclopropyl cations also has been investigated159,161,162 [Eq. (3.35)]. 

This chapter focuses on the use of silver(I) salts as Lewis acids in the ring-opening reactions of halocyclopropanes. Both the classical and most recent examples of this type of chemistry are examined with emphasis on the use of this simple transformation to build up complex intermediates that are potentially useful in the construction of natural products. 

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