Cleavage of aziridines

Cleavage of aziridines has been employed in the asymmetric total synthesis of pancratistatin 57 [47], a compound that is the object of considerable attention thanks to its broad spectrum of antineoplastic activities [48]. The chemistry of vinylaziridines has for the most part been confined to their use in rearrangement sequences resulting in functionalized pyrrolines. Hence, because of the lack of data concerning the ring-opening of vinylaziridines with carbon nucleophiles,... 

Oxiranes and aziridines are reduced to alcohols and amines, respectively, for example by Ni/H2, Zn-NH4C1, P-I, Al-Hg, Na/NH3, Li/EtNH2 (7UOC330). Cleavage of aziridines with lithium naphthalenide provides synthetically useful dianions as shown in Scheme 29 (93TL1649,94JOC3210). 

Cleavage of aziridines. Aziridine-2-carboxylic esters undergo ring opening to... 

Copper(II) Inflate. 19, 112 20, 122-123 Cleavage of aziridines. Coppenlli aziridines by arylamines. 

Cleavage of aziridines. Copper(II) triflate is a good catalyst for cleavage of... 

A computational study of the effect of substituents on the rate of conrotatory thermal cleavage of aziridine has been reported and while the parent compound has a high free energy of activation, this can be lowered by substituent effects. Anionic species are effective in increasing the calculated reaction rate." Quantum dynamical results of the pericyclic rearrangement of cyclooctatetraene have been compared with the traditional scheme of fluxes of electrons in pericyclic orbitals. Pentadienyl cation electrocyclizations have been reviewed. ... 

Reddy, M.A., Reddy, L.R., Bhannmathi, N. and Rao, K.R., An efficient biomimetic cleavage of aziridines with nucleophiles catalyzed by cyclodextrin in water, Chem. Lett., 2001, 246-247. 

Oxidative cleavage of P-aminoacyl complexes can yield P-amino acid derivatives (320,321). The rhodium(I)-catalyzed carbonylation of substituted aziridines leads to P-lactams, presumably also via a P-aminoacyl—metal acycHc compound as intermediate. The substituent in the aziridine must have 7T or electrons for coordination with the rhodium (322,323). 

Amino alcohols are also good substrates for aziridination under Mitsunobu conditions. The rfs-1,4-amino alcohols 48, obtained by reductive cleavage of the nitrogen-oxygen bonds of the hetero Diels-Alder adducts 47, underwent syn-SN2 -type displacement on treatment with PPh3 and DEAD to give cyclic vinylaziridines 49 (Scheme 2.15) [27]. 

Intramolecular and intermolecular 1,3-dipolar cycloadditions of aziridine-2-car-boxylic esters with alkenes and alkynes have been investigated [131, 132]. Upon heating, aziridine-2-carboxylates undergo C-2-C-3 bond cleavage to form azome-... 

Microwave irradiation in solvent-free conditions induces the cleavage of the 2,3-bond of 2-aroyl-aziridines 135 to give an azomethine ylide intermediate, which subsequently undergoes cycloadditions to a multiple bond and leads to oxazolidine, imidazoline, naphthooxazole and pyrroline derivatives 136 in good yields (Scheme 9.41) [32b], Reactions were performed at atmospheric pressure in an Erlenmeyer flask placed in a commercial domestic oven. The reactions were complete in 10-15 min while the conventional method requires 18-20 h. 

Ejection of dinitrogen from the triazoline adducts to form the related aziridines was promoted by ultraviolet irradiation (300 nm, benzene) and usually proceeded in excellent yield. An exception was found in the irradiation of the triazoline substrate 59, where cleavage of the cyclobutane ring occurred as the dominant reaction pathway to form the pyridazino norbomadiene 61 (and secondary photoproducts derived therefrom), together with the triazole-4,5-diester 62. A role for the pyridazine ring and the 2-pyridyl substituents in stabilising the diradical intermediate 60 has been proposed for this abnormal outcome (Scheme 8). 

Oxidative cleavage of the C(l)—C(2) bond of aziridines and 2-amino-1-cycloal-kanols, giving the corresponding keto... 

The production of 69 and 70 in this photoreaction is in accord with the operation of mechanistic pathways involving the generation and competitive cleavage of aziridinyl-dicarbinyl biradical 71 (Scheme 12). Thus, the major photoproduct 69 is formed by C—N bond cleavage in 71 (path a). The alternative fragmentation of the C—C bond in 71 affords intermediate 72, which cyclizes yielding aziridine 70 (path b). As such, this represents the first example of a 2-aza-di -rr-methane (2-ADPM) rearrangement that occurs via a three-membered-... 

The [3 -f 2] cycloaddition of aziridines and dipolarophiles, like dimethyl acetylenedicarboxylate or dimethyl fumarate and maleate, was investigated by Gaebert and Mattay. Via C—C and C—bond cleavage five-membered heterocycles are formed in moderate yields. The different product ratios dependent on the reaction conditions (PET/direct excitation/thermal reaction) gave insights to the reaction details and are summarized in the proposed mechanism (Scheme 52) [84],... 

Diazoesters 22 have an electronically unique a-carbon atom. (Scheme 9) They are commonly used for the formation of aziridines 23 from imines 24. The intermediate (25) resulting from the addition of a-diazoesters 22 to the latter (24) can undergo elimination of the proton at the a-position prior to extrusion of molecular nitrogen. This interrupted aza-Darzens reaction allows for the direct alkylation of diazoesters 22 via cleavage of a carbon-hydrogen bond. 

Lewis acid-promoted [3+2] cycloadditions of aziridines and epoxides proceeding via carbon-carbon bond cleavage of three-membered ring heterocycles are demonstrated for the first time. This proposal details plans for extending these initial results into a general synthetic method for the enantioselective synthesis of structurally diverse pyrrolidine- and tetrahydrofuran-containing organic compounds. Expected outcomes of the proposed work will include... 

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