Paper
Addition of bromine chloride and iodine monochloride to carbonyl-conjugated, acetylenic ketones: synthesis and mechanisms.
Published 2002 · Victor L Heasley, Deanna M Buczala, Alfred E Chappell
The Journal of organic chemistry
17
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Abstract
The reactions of 3-butyn-2-one (1), 3-hexyn-2-one (2), and 4-phenyl-3-butyn-2-one (3) with bromine chloride (BrCl) and iodine monochloride (ICl) in CH(2)Cl(2), CH(2)Cl(2)/pyridine, and MeOH are described. The data show that the major products in CH(2)Cl(2) are (Z)-AM (anti-Markovnikov) regioisomers. With the exception of 3 and ICl, the (E)-AM regioisomers predominate when pyridine was added as an acid scavenger. Minor amounts of the M regioisomers were formed with 1 and 2 and BrCl. The percentage of M regioisomer increased significantly with 1 and BrCl in MeOH, but MeOH had little affect on the other reactions. Isolation and stability of the products are discussed. Detailed evidence for the structures of the products, involving a combination of MS, (1)H and (13)C NMR, and IR, is presented; HRMS analyses are provided as proofs for all of the products. The acid-catalyzed mechanism and the halonium ion mechanism are considered as possible pathways in the formation of the products.
Bromine chloride and iodine monochloride can form various regioisomers in carbonyl-conjugated ketones, with (Z)-AM regioisomers dominating in CH(2)Cl(2) and (E)-AM regioisomers in MeOH
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