On the Reaction of N-Bromoacetamide with Olefins. Preparation and Chemistry of 2-Bromo-N-Bromoacetimidates, a New Class of Compounds

Abstract

A historical and mechanistic review of the Wohl-Ziegler reaction (allylic bromination by N-bromoamides and imides) is presented as an introduction to the present work, a re-examination of the reaction of N-bromoacetamide (NBA) with some olefins. The reaction has been found to lead not to allylic bromination but, rather, to 2-bromo-N-bromoacetimidates, a new class of compounds. The stoichiometry of the reaction is: olefin + 2 NBA + adduct + acetamide. The process appears to occur in two stages, viz., a free radical reaction of NBA with itself to form N,N-dibromoacetamide (NDBA), followed by ionic addition of NDBA to the double bond. Hofmann's synthesis of NDBA has been repeated; the compound reacts rapidly with cyclohexene to give the same adduct 10 as does NBA. A variety of stereochemical and selectivity data suggest that this is an ionic addition.The chemical transformations of 2-bromo-N-bromoacetimidates under thermal, acidic, and basic conditions are discussed.Comme introduction au present travail qui est un reexamen de la reaction de la N-bromoacetamide avec quelques olefines, nous presentons une revue historique et mecanistique de la reaction de WohlZiegler (bromuration allylique par des N-bromoamides et imides). On a trouve que la reaction ne conduit pas B la bromination allylique mais plut8t aux bromo-2 N-bromoacCtimidates, une nouvelle classe de composes. La stoichiometrie de la reaction est: olefine + 2 NBA + compose d'addition + acetamide. Le processus semble se produire en deux temps a savoir une reaction radicalique de la NBA sur elle-mCme pour conduire a la N,N-dibromoacktamide (NDBA) suivie d'une addition ionique de la NDBA a I'alcene. La synthese de Hofmann de la NDBA a it6 repitee; ce compose reagit rapidement avec lecyclohCxCne et conduit au produit 10 qui est aussi obtenu sous I'action de la NBA. La steriochimie et la sClectivitC de cette reaction suggerent que I'addition est ionique.On discute aussi des transformations chimiques que subissent les bromo-2 N-bromoacCtamidates sous I'influence de la chaleur, des acides, et des bases.

The photochemical addition of N-haloamides to olefins: the influence of various factors on the competition between 1,2-addition and hydrogen abstraction

“…The effect is less important in the case of NCA (16) (entries 9 and 10) than in the case of N-bromoacetamide (NBA, l a ) (entries 1 to 5) and N-bromochloroacetamide (In) (entries 6 and 7).11 Thus very high yields of addition can be obtained with simple N-bromo-N-hydrocarboxamides. The 91% yield of addition with NBA is particularly worth noting since the photolysis in refluxing carbon tetrachloride was reported to give, as the primary product, trans-2-bromocyclohexyl-N-bromoacetamidate resulting from the ionic addition of N,N-dibromoacetamide and only 1% of trans 1,2-adduct 3a (28). The temperature has little influence on the cis(2)ltrans(3) ratio.…”

Synthesis and theoretical activity of three steroid-derivatives on both aromatase and 17β-hydroxysteroid dehydrogenase Type 1 enzymes

“…13 Second stage. Some reports have showed the preparation of several acetimidic acid derivatives using some reagents such as 2bromocyclohexylacetimidium chloride [32], N-benzyl-N-nitro-sopivalamide [33], o-aminobenzoylhydrazine [34]. Analyzing these data and a report which showed the synthesis of a steroidethanimidic acid derivative [35]; in this study an azahexacyclotetracosa-ethanimidic acid (3) was prepared from compound 2 and acetonitrile ( Figure 1).…”

Preparation of Imino Lactones by Electrophilic Cyclization of β,γ‐Unsaturated Hydroxamates: Formation of 3‐Cyanoprop‐2‐en‐1‐ones through Fragmentation Reactions

“…A similar reaction leading to the formation of 2-bromocyclohexanone and acetonitrile has been reported. [14] The abstraction of the mobile hydrogen α to the oxygen atom seems to be the key step of this reaction. Indeed, we did not observe this fragmentation on successive treatment of hydroxamate, formed from (3E)-hex-3-enoic acid, with bis-(collidine)bromine(I) hexafluorophosphate and triethylamine.…”