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

Abstract

Abstract:The regio-and stereoselective aminobromination of a,b-unsaturated carbonyl compounds and simple olefins catalyzed by elementary aluminium powder has been established by using p-toluenesulfonamide (TsNH 2 ) and N-bromosuccinimide (NBS) as the nitrogen/bromine sources. The reaction was convenient to carry out with a loading of 1 mol% catalyst at room temperature without inert gas protection. This method provides an easy approach to trans vicinal haloamino derivatives of a,bunsaturated carbonyl compounds and simple olefins in high yields (up to 99.8%) and in excellent regioand stereoselectivities. The electron-rich and electron-deficient olefins show significant differences in activity to the aminobromination reaction and give the opposite regioselectivities. Two possible pathways involving separately a bromonium or an aziridinium intermediate have been proposed.

Hypervalent Iodine (III) Catalyzed Regio- and Diastereoselective Aminochlorination of Tailored Electron Deficient Olefins via GAP Chemistry

“…Based on experimental observations and our as well as others' previous works (Li et al, 2001;Wei et al, 2001;Wang and Wu, 2007;Wu and Wang, 2008;Chen et al, 2009), a rational mechanism for the formation of 13 and 14 is illustrated in Scheme 6. 4-TsNCl 2 on reaction with 4-TsNH 2 may produce N-chloro-p-toluenesulfonamide (4-TsNHCl) 15, which might be oxidized by PhI OAc (Kikugawa et al, 2003;Murata et al, 2008) Typical procedure: Into a dry vial, 11 or 12 (1.5 mmol, 1 eq), 4-TsNCl 2 (3 mmol, 2 eq) 4-TsNH 2 (3 mmol, 2 eq), PhI(OAc) 2 (20 mol%), and freshly activated 4 Å molecular sieves (150 mg) were added.…”

Catalytic Asymmetric Bromoamination of Chalcones: Highly Efficient Synthesis of Chiral α‐Bromo‐β‐Amino Ketone Derivatives

“…Furthermore, the trans ‐α‐bromo‐β‐amino products obtained indicated that the aziridinium‐based mechanism9a was also unlikely. The observations of the high anti stereoselectivity and formation of trace amounts of dibromide product indicate that a possible bromonium intermediate4, 9e is likely. Secondly, HRMS analysis on the catalyst structure showed that [ L3 /Sc(OTf)] + was the main fragment ion, and nonlinear effects14 were not observed, which indicates that the monomeric catalyst should be the main catalytically active species.…”

The combination of benzamides/NCS as nitrogen/halogen sources for aminohalogenation of β-nitrostyrenes resulting in dichlorinated haloamides

“…The regioselectivities of the reaction were completely controlled, and solely one regio-isomer was observed for all these cases. Careful 1 H NMR analysis of the products revealed that the chlorine moiety was attached to the α-carbon position of nitroalkane instead of the β-carbon position as encountered in nearly all of the previous cases where the electron-withdrawing olefins were employed [32][33][34][35][36][37][38].…”