Aziridines azetidines

The ORD curves and ECD spectra of a number of chiral methyl-substituted cyclic amines, aziridine, azetidine, pyrrolidine and piperidine, and their A-mcthyl, A-halo and A-cyano derivatives, and of (5 )-l-azabicyclo[3.1.0]hexane [(5 )-115] were measured96. 

Azetidine can be considered as a fairly typical cyclic amine. Strain in the four-membered ring is less than that in the three-membered aziridine system, and as a result azetidines show few, if any, of the exceptional properties associated with aziridines. Thus, ring cleavage reactions occur with greater ease than in larger ring cyclic amines, but much less readily than with aziridine for example, unlike aziridines, azetidines do not function as alkylating... 

A somewhat similar ring closure in which a nitrogen anion attacks a halogenated carbon center is obtained in the anodic oxidation of dimethyl Q -(it -tosylaminoalkyl) malonates in methanol containing KI in an undivided cell. Aziridines, azetidines, and pyrrolidines may be formed in good yield [63]. 

Nitrato-N-nitramines. A soln. of startg. aziridine in methylene chloride treated with 1.25 eqs. N2O5 at -10 to —5° for 0.5 to 1 h - product. Y 70%. Reaction is only applicable with strained N-heterocyclics (aziridines, azetidines). F.e.s. P. Golding et al., Tetrahedron Letters 29, 2735-6 (1988). 

Two cyclic olefins were resolved by coordination with dicarbonyl Rh(I)-3-tri-fluoroacetyl-lR-camphorate [23, 24]. Starting with this observation, Schurig and coworkers [25] have systematically explored stereoselective partitioning on optically active -diketonates of transition metals, and have extended the use of these selectors to the chiral differentiation of underivatized ketones and alcohols and to heterocyclic compounds such as oxiranes, aziridines, azetidines, thiiranes, tetrahy-drofuranes, etc. 

The compounds in this section are similar to the others in chapter seven, but a nitrogen, oxygen or a sulfur is incorporated in the ring. Since most cases involve a nitrogen, however, the final products are usually substituted aziridines, azetidines, pyrrolidines, piperidines, or hexahydroazepines with a carboxyl group pendant to the ring. Many synthetic strategies are unique to this class of amino acids. 

This chapter deals with recent developments in "on-water" synthetic approaches to small (3-4) and medium (5-7) size aza-heterocycles of biological relevance. Selected examples of syntheses of aziridines, azetidines, 2-azetidinones, pyrroles, pyrazoles, imidazoles, benzimidazoles, indoles, pyridines, pyrimidines, quinolines, azu-lenes, and azepinones are described. A brief introductory paragraph on significance of each class of compoxmd is followed by its common S5mthetic methods. The role of water and mechanism of novel reactions will be discussed where applicable. 

Compared with aziridines, azetidines are rather less abundant structural units, foimd in few natural products possessing important biological activities. Many routes are... 

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