Brian J. Kelly

Aziridination by oxidative addition of N-aminoquinazolones to alkenes: Evidence for non-involvement of N-nitrenes

Abstract Oxidation of 3-aminoquinazolones e.g. (22) with lead tetra-acetate at −20°C gives N -acetoxyaminoquinazolones e.g. (23) which are stable in solution at this temperature. These N -acetoxyaminoquinazolones function as inter- and intramolecular aziridinating agents for alkenes and appear to be playing the role previously ascribed to the corresponding N -nitrenes. An analogous N -acetoxyaminophthalimide intermediate (31) is implicated in the lead tetra-acetate oxidation of N -aminophthalimide (4).

Amination with 3-acetoxyaminoquinazolin-4-(3h)ones: preparation of α-aminoacid esters by reaction with silyl ketene acetals followed by NN bond cleavage

Abstract Solutions of 3-acetoxyaminoquinazolinone (5) react with enol ethers and silyl ketene acetals to give α-aminoaldehyde α-aminoketone or α-aminoacid derivatives. Acylation of the exocyclic nitrogen in these derivatives, as a preliminary to reductive N  N bond cleavage, could only be accomplished by indirect means. Samarium diiodide, however, effected the reduction of this N  N bond without the necessity for N -acylation. Solutions of the corresponding enantiopure 3-acetoxyaminoquinazolinone (34) brought about the diastereoselective amination of the prochiral silyl ketene acetal (15) and reductive N  N bond cleavage of the major diastereoisomer lead to enantiopure 2-phenylalanine methyl ester.

Aziridine-azirine transformation by 1,2-elimination via an aziridinyl carbanion intermediate

Abstract Desilylation of aziridine (5) by treatment with cesium fluoride in dry dimethylformamide in the presence of benzaldehyde followed by oxidation with manganese dioxide gives the benzoylaziridine (11) in 80% yield: in the absence of benzaldehyde, the presumed aziridinyl carbanion intermediate (9) gives the aziridine (7) (58%).

Aziridination of alkenes by 3-amino-2-ethylquinazolin-3H-4-one and lead tetra-acetate-trifluoroacetic acid

Abstract A number of alkenes undergo aziridination in good yield by oxidative addition of the title N -aminoquinazolone (1) only in the presence of TFA.

Reactions of enol ethers and silyl ketene acetals with 3-acetoxyamino-2-ethylquinazolin-4(3H)-one: cleavage of N–N bonds in 3-alkylaminoquinazolin-4(3H)-ones

Treatment of enol ethers and silyl ketene acetals with the N-acetoxyaminoquinazolone 1 gives α-aminoaaldehyde, α-aminoketone or α-aminoacid derivatives in good yields: cleavage of the N–N bond in 3-alkylaminoquinazolinone derivatives can be accomplished by samarium diiodide in tetrahydrofuran.

Aziridination of alkenes using 3-amino-2-ethylquinazolin-4(3H)-one and lead tetra-acetate–trifluoroacetic acid

Efficient aziridination of terminal alkenes by oxidative addition [lead tetra-acetate (LTA)] of the N-aminoquinazoline (1) is effected by inclusion of trifluoroacetic acid (TFA) in the mixture. The effect of (a) substitution of either lead tetratrifluoroacetate or [bis(trifluoroacetoxy) iodo]benzene for LTA or (b) addition of preformed N-acetoxyaminoquinazolone (7) to allyl chloride in the presence of TFA, suggests that the major factor in bringing about improved aziridination yields of allyl chloride and other unreactive alkenes is protonation of the quinazolone ring.

Aziridination of cyclohex-2-en-1-ol and geraniol: comparison with epoxidation

Aziridination of cyclohex-2-en-1-ol with 3-acetoxyamino-2-ethylquinazolone (1) is highly stereoselective, and reaction with geraniol is highly regioselective for the allylic alcohol double bond; comparisons are made with the corresponding reactions of peracids.

Oxidation of N-aminoquinazolones in the presence of alkenes: evidence against involvement of N-nitrenes

Solutions of 2-ethyl-3-acetoxyamino-4(3H)-quinazolone (6) have been obtained by oxidation of the corresponding 3-aminoquinazolone (4) with lead tetra-acetate at –20 °C; (6) brings about aziridination of alkenes by a mechanism that does not involve N-nitrene or N-nitrenium ion intermediates.

Aziridination of cyclohex-2-enols and 3-substituted cyclohexenes: comparison with epoxidation

Aziridination of cyclohex-2-enol, 3-methylcyclohex-2-enol, and 3-phenylcyclohex-2-enol with 3-acetoxyamino-2-ethylquinazolin-4(3H)-one (4) proceeds with high stereoselectivity syn to the hydroxy group to give compounds (7), (19), and (21), respectively in good yields. These results are analogous to the epoxidations of these alkenes using peracids. Aziridinations of cyclohex-2-enyl acetate or cyclohex-2-enyl methyl ether proceed stereospecifically anti to the acetoxy or methoxy group to give (11) and (17), respectively, but in low yield. These results are in contrast to the epoxidations of these alkenes using peracids.The configurations assigned to these products are supported by an analysis of the n.m.r. spectra of 2-substituted 7-azabicyclo[4.1.0] heptanes.

Evidence for phthalimidonitrene as a common intermediate in several extrusion reactions

A common intermediate, presumably phthalimidonitrene 1, is generated in the thermolysis of the aziridinobenzofurans 3(R = Ac, CO2Me, Bz, COBut and CN) as well as the sulphimide 4, and the azabenzonorbornadiene 5. The transfer of 1 shown in Scheme 1 is zero order in 2-acetylbenzofuran providing further evidence against a concerted bimolecular mechanism 10 for ‘nitrene’ transfer.