Categories: C-Cl Bond Formation >
Synthesis of 1,2-dichloroalkanes
An operationally simple triphosgene-pyridine activation enables the conversion of unactivated terminal aliphatic epoxides to alkyl vicinal dichlorides. The methodology tolerates a broad of scope of substrates as well as protecting groups. Furthermore, these mild conditions generally yield clean reaction mixtures that are free of byproducts upon aqueous workup.
A. H. Cleveland, F. R. Fronczek, R. Kartika, J. Org. Chem., 2018, 83, 3367-3377.
A stereospecific triphenylphosphine oxide-catalyzed 1,2-dichlorination reaction of epoxides is effective for a range of terminal and internal epoxides. In contrast to the classical Appel-type dichlorination of epoxides, oxalyl chloride is used as a stoichiometric reagent to generate the chlorophosphonium salt responsible for dichlorination from catalytic triphenylphosphine oxide.
R. M. Denton, X. Tang, A. Przeslak, Org. Lett., 2010, 12, 4678-4681.
A Ph3P/I--promoted dihalogenation of epoxides provides 1,2-dihalides in the presence of XCH2CH2X (X = Cl or Br) as the solvent and halogen source. All reagents are widely available and easy to handle. The protocol offers mild conditions and operational simplicity.
J. Long, J. Chen, R. Li, Z. Liu, X. Xiao, J.-H. Ling, X. Zheng, J.-C. Xiao, Synlett, 2019, 30, 181-184.
The use of Selectfluor as an oxidant and tetrabutylammonium bromide/chloride salts as a halogen source enables a metal-free and molecular halogen reagent-free dihomohalogenation methodology. This effective strategy provides various fluorine-free halogenated products easily in quantitative yields from alkenes, alkynes, and natural products.
Z. Dağalan, R. Koçak, A. Daştan, B. Nişancı, Org. Lett., 2022, 24, 8261-8264.
A Mn-catalyzed electrochemical dichlorination of alkenes with MgCl2 as the chlorine source provides an operationally simple, sustainable, and efficient access to a variety of vicinally dichlorinated compounds. In particular, alkenes with oxidatively labile functional groups, such as alcohols, aldehydes, sulfides, and amines, were transformed into the desired vicinal dichlorides with high chemoselectivity.
N. Fu, G. S. Sauer, S. Lin, J. Am. Chem. Soc., 2017, 139, 15548-15553.
A mild and efficient protocol enables the preparation of 1,2-dichloroalkane derivatives from olefins in the presence of NH4Cl and Oxone at room temperature. Various terminal, internal, and cyclic alkenes reacted smoothly to give the corresponding dichlorinated products in good to excellent yields. Internal olefins dichlorinated with moderate to excellent diastereoselectivity.
P. Swamy, M. M. Reddy, M. A. Kumar, M. Naresh, N. Narender, Synthesis, 2014, 46, 251-257.