Addition of Bromine Chloride and Iodine Monochloride to Carbonyl-Conjugated, Acetylenic Ketones:  Synthesis and Mechanisms

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 CH2Cl2, CH2Cl2/pyridine, and MeOH are described. The data show that the major products in CH2Cl2 are (Z)-AM (anti-Markovnikov) regioisomers. With the ex...

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Veröffentlicht in:Journal of organic chemistry 2002-04, Vol.67 (7), p.2183-2187
Hauptverfasser: Heasley, Victor L, Buczala, Deanna M, Chappell, Alfred E, Hill, David J, Whisenand, Josh M, Shellhamer, Dale F
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Sprache:eng
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Zusammenfassung: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 CH2Cl2, CH2Cl2/pyridine, and MeOH are described. The data show that the major products in CH2Cl2 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, 1H and 13C 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.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo011031v