Transition Metal-Catalyzed Regio- and Stereoselective Aminobromination of Olefins with TsNH₂ and NBS as Nitrogen and Bromine Sources

Abstract

[reaction: see text] A new synthetic procedure for aminohalogenation of olefins has been developed for the preparation of vicinal haloamine derivatives in high yields by using Cu, Mn, or V catalysts with p-toluenesulfonamide (TsNH(2)) and N-bromosuccinimide (NBS) as nitrogen and bromine sources, respectively. Unprecedented regio- and stereoselectivity (anti:syn > 99:1) toward the aminohalogenation process is shown for olefinic substrates as well as transition metal catalysts.

Aluminium Powder‐Catalyzed Regio‐ and Stereoselective Aminobromination of α,β‐Unsaturated Carbonyl Compounds and Simple Olefins with the p‐Toluenesulfonamide/ N‐Bromosuccinimide (TsNH2‐NBS) System

“…Ethyl 4-methoxycinnamate (24a), for example, afforded the reversed regioisomer, as confirmed by MS analysis and by comparing its melting point and NMR data with literature values. [5] Contrarily, an a,bunsaturated ester without a methoxy group positioned on the benzene ring para to the double bond, i.e., ethyl cinnamate (23a), afforded the "normal" regioisomer under the same reaction conditions.…”

“…There was no explanation for these observations although they have been found in a few examples previously reported. [5,9] It seems reasonable to believe there are two possible pathways of the present aminobromination existing during the reaction process: a bromonium intermediate and an aziridinium intermediate formation pathway.…”

“…[5] For the second step, the negative p-toluenesulfonamide would be produced from negative succinimide by reacting with p-toluenesulfonamide [Scheme 2, Eq. (2)].…”

“…[14] We found that the reaction of NBS and TsNH 2 in CH 2 Cl 2 for 24 h gave an equilibrium mixture of NBS (major), TsNH 2 (major), N-bromo-p-toluenesulfonamide {TsNHBr 1, which had been isolated and characterized by 1 H and 13 C NMR and MS in the reaction of TsNH 2 with NBS. [5] ), TsNBr 2 2 (minor), and succinimide [Eq. (4) and Eq.…”

“…[2] Since several new systems for the aminohalogenation of electron-deficient olefins have been successfully established by Li and others, [1.3,4] the interest in this reaction has been renewed and many exciting catalytic systems have been developed. Recently, Sudalai and co-workers [5] developed a more facile and efficient method for the aminobromination of a large range of olefins with the combination of p-toluenesulfonamide (TsNH 2 ) and N-bromosuccinimde (NBS) using transition metals salts such as CuI, V 2 O 5 , MnSO 4 , and MnA C H T U N G T R E N N U N G (III)-salen as catalysts.…”