Azirines from aziridines

Exposure of an azirine to carbon monoxide in the presence of a catalytic amount of [Pd(PPh3)4] gives the bicyclic P-lactam (23) in reasonable yield. Attempts to synthesize monocyclic P-lactams from azirines has so far failed, but aziridines can be carbonylated to -lactams. )epending on the organome-tallic reagent used two different products can be obtained (Scheme 26). Using catalytic quantities of [Rh2(CO)4Ch] carbon monoxide inserts selectively into the more-substituted C—N bond, whereas using a stoichiometric amount of [Ni(CO)4] it is the less-substituted C—N bond that is carbonylated. ... 

A number of examples of imidazole synthesis from azirines and aziridines have been included under other classifications (see Sections 3.02.8.1.l(iii) and 3.02.8.1.2(i),(ii)). 2/f-Azirines are intermediates in the rearrangement of oximino p-toluenesulfonates to aminoketones in the presence of bases, and with 2-acylphenols these azirines form imidazolones. 4//-Imidazoles (244) are formed when a 2-amino-3,3-dimethylazirine reacts with an acetamide (Scheme 181) <90CHE719>. 

Aziridines from oximes or from a-haloimines via azirines (see 1st edition). 

Preparative routes to aziridines and 1-azirines are derived from cycloelimination processes in which one, and sometimes two, bonds are formed directly to the nitrogen atom (Scheme 1). For aziridines these include the two intramolecular cyclization pathways involving either nucleophilic displacement by the amine nitrogen (or nitrenium anion) on the /3-carbon (route a) or nucleophilic displacement by a /3-carbanionic centre on the amine nitrogen... 

Azirines (three-membered cyclic imines) are related to aziridines by a single redox step, and these reagents can therefore function as precursors to aziridines by way of addition reactions. The addition of carbon nucleophiles has been known for some time [52], but has recently undergone a renaissance, attracting the interest of several research groups. The cyclization of 2-(0-tosyl)oximino carbonyl compounds - the Neber reaction [53] - is the oldest known azirine synthesis, and asymmetric variants have been reported. Zwanenburg et ah, for example, prepared nonracemic chiral azirines from oximes of 3-ketoesters, using cinchona alkaloids as catalysts (Scheme 4.37) [54]. 

Carbon-centered radicals have been shown to undergo addition reactions with azirine-3-carboxylates. Methyl 2-(2,6-dichlorophenyl)azirine-2-carboxylate thus reacts with alkyl and aryl iodides in the presence of triethylborane to give aziridines in good yields. The radical approaches from the opposite face to the aryl substituent, giving the cis products as single diastereoisomers (Scheme 4.43) [63],... 

The first compound is an antibiotic isolated from Streptomyces aureus [20], while the second compound is a cytotoxic antibiotic isolated from Dysidea fragilis, a marine sponge [21]. A logical approach to the synthesis of azirines would be an elimination reaction of a suitably M-substituted aziridine. Thus, AT-chlorination of aziridine-2-carboxylic esters was carried out using ferf-butyl hypochlorite (Scheme 8). 

The Swern oxidation was also employed by Davis and McCoull [251 for the synthesis of 2iT-azirinephosphonates 27 and 28 from the corresponding aziridines 26 (Scheme 14). Interestingly, in this case a mixture of the regioiso-meric azirines is obtained, whereby the proton abstraction adjacent to the phos-... 

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