Dihalooxygenation of Alkynes and Alkynols: Preparation of 2,2-Dihaloketones and gem-Dihalolactols

Abstract

A mild and convenient method for the synthesis of 2,2-dihaloketones and gem-dihalolactols has been developed. For the synthesis of 2,2-dihaloketones, alkynes were employed as substrates to react with halogenating agents, Cl2 or ClBr, which were generated in situ from aqueous HCl and NCS or aqueous HCl and NBS. On the other hand, gem-dihalolactols could be prepared from alkynol substrates using the same reaction conditions. This method could be applied to a broad range of substrates to give the corresponding products in low to good yields.

Alkyne Oxidation by a Vitamin B2-Based Photocatalytic System with Both H2O and O2 as the Oxygen Source

“…To gain more insights into the mechanism, the other question was to probe the function of the chloride anion (Cl – ). Previously, the electrophilic “Cl + ” species was proposed as the responsible species in the stoichiometric or catalytic dihalo-oxygenation of alkynes, respectively . However, as can be seen from Scheme a, only trace amounts of α-chloroketone ( c1 ) or α,α-dichloroketone ( c2 ) were found even with an excess amount of chloride source in this case.…”

Additive-free oxychlorination of unsaturated C–C bonds with tert-butyl hypochlorite and water

“…2 On the one hand, in the case of oxychlorination of alkynes, the α,α-dichloroketone products could be accessed with various chlorine sources. For example, classic electrophilic chlorine compounds including N -chlorosuccinamide (NCS), 3-dichloro-5,5-dimethylhydantoin (DCDMH), and trichloroisocyanuric acid (TCCA) have been used to enable the synthesis of gem -dichloroketones from alkynes in the presence of catalysts 3 or under acidic conditions 4 (Scheme 1a(i)). At the same time, the oxy-1,1-dihalogenation of alkynes has been achieved by the combination of stoichiometric amounts of inorganic chloride and artificial oxidants, such as Oxone, persulfate, and organic iodine( iii ) compounds, 5 or the use of strong chlorinating reagents alone like TCCA 6 (Scheme 1a(ii)).…”