Imine radicals

MeON=CH(CH2)3CHO with BusSnH and AIBN, for example led to trans-2-(methoxyamino)cyclopentanol in good yield.Addition of radical to the C=N unit of R—C=N—SPh or R—C=N—OBz led to cyclic imines. Radical addition to... 

The carbon-nitrogen double bond in imines is reduced at less negative potentials than the corresponding carbonyl function. Also imine radical-anions are more basic than carbonyl radical-anions. Imines with at least one phenyl substituent on the carbon-nitrogen double bond are sufficiently stable for examination in aprotic solvents and reversible one-electron reduction of benzaldehyde anil [179] or benzophenone anil [ISO] can be demonstrated with rigorous exclusion of moisture. 

Because they are isoelectronic, it is reasonable to expect that imine radical anions (>C=N— ) would exhibit chemistry analogous to that of >C=0. Such does appear to be the case, based upon the limited information available. 

Imine radical anions appear to be substantially more basic than their ketyl anion counterparts. In 1991, Zhan and Hawley reported that Ph2C=NH (generated via the electrochemical reduction of benzophenone imine) was a sufficiently strong base to depro-tonate weak carbon acids whose pK values were as high as 33185. 

Studies of ammonia synthesis on iron catalyst suggest that the reaction occurs through surface imine radicals. 

No agreement on the nomenclature for these neutral, univalent nitrogen intermediates was achieved for a long time. The names used include imene 14>, imine radical 15 16), azene 17>, azacarbene 18J, imin 19> and nitrene 20>. The nitrene nomenclature, which parallels that for carbenes, is commonly used today and will be employed in this article. In this nomenclature H—N is nitrene, CeHg—N is phenylnitrene, CH3—0—C—N is methoxycarbonylnitrene etc. 

C-C bond formation in inter- or intramolecular additions starting with olefin [ 199, 200], ketyl [201] (generated by PET [202], chemical or cathodic [24, 203] reduction) [204, 205] or imine radical anions [206] has become a versatile method. In general, the intramolecular addition is highly suitable for the construction of five membered rings, less so for six-, and not effective for seven-membered ring formation. 

Radical cyclization is not limited to reaction with a C=C unit (see 15-29 and 15-30), and reactions with both C=N and C=0 moieties are known. Reaction of MeON=CH(CH2)3CHO with Bu3SnH and AIBN, for example, led to trans-2-(methoxyamino)cyclopentanol in good yield.Conjugated ketones add to aldehyde via the p-carbon under radical conditions (2 equivalents of Bu3SnH and 0.1 equivalent of CuCl) to give a p-hydroxy ketone.Addition of radical to the C=N unit of R C=N SPh ° or R—C=N—led to cyclic imines. Radical addition to simple imines leads to aminocycloalkenes. Radical also add to the carbonyl unit of phenylthio esters to give cyclic ketones. 

The reaction was discovered in 1923 in interesting circumstances. Products from the decomposition of hydrazoic acid in various solvents were investigated and the decomposition catalysed by sulphuric acid in benzene was found to lead to aniline Schmidt considered an imine radical NH to be the species responsible and on attempting to trap this with benzophenone he obtained benzamide. The reacdon was generalized and rapidly exploited, mainly by its discoverer. The currently accepted mechanism was proposed in outline shortly after-wards and is shown in its modern form in scheme (19) for carboxylic... 

Ketimine radicals. Ketoximes are deoxygenated on treatment with sulfinyl chlorides via homolysis of the oxime sulfinates. When suppression of diradical recombination by steric hindrance is exploited, imine radical intermediates tend to undergo other reactions such as intramolecular addition. 

Nuclear hyperfine structure was observed and analysed in both the naturally abundant SO and SeO, but to illustrate the principles we turn to another E system, the imine radical (NH) studied by Wayne and Radford [58] using far-infi ared laser magnetic resonance. The spectra of NH and ND show hyperfine structure from aU the... 

A. Laskin and A. Lifshitz, Thermal decomposition of quinoline and isoquinoline the role of 1-indene imine radical, J. Phys. Chem. A 102, 928-946 (1998). 

Efforts to produce the cyclopropylamino-radical for e.s.r. studies gave only ring-opened imine radicals. Ring-openings of cyclopropyl, cyclobutyl, and bicyclo[n,l,0]alkyl radicals have been reported and the disrotatory nature of the ring-opening of cyclopropyl radicals has been established by examination of ring-fused systems. ... 

SET with A -sulfonyl aldimine to form imine radical anion. In the presence of chiral ionic Bronsted acid catalyst, the resulting A -sulfonyl aldimine radical anion prefers to form a chiral ion pair. The radical-radical heterocoupling of a-aminoalkyl radical with chiral ion pair-based anion radical affords 1,2-diamine derivatives in high enantioselectivties. 

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