Molecular-orbital calculations aziridines

Computed atomic charges and binding energies from an INDO molecular orbital study of a-heteroatom nitrenes are consistent with their known reactivity towards olefins to give aziridines. Molecular orbital calculations on the reaction of propylene oxide and isobutylene oxide with hydrogen chloride and ammonia predict an orientation of addition in agreement with experiment. 

However, contrary to rmstrained lactams and amides, it has been demonstrated by ab initio molecular orbital calculations optimized at the 6-3IG level that the protonation site is a funaion of the distortion of the amide linkage. Indeed, in aziridin-2-one (4) and in bridgehead bicydic laaams, for example, l-azabicydo[2.2.2]octan-2-one (2-quinuclidone) (5) and l-azabicydo[3.3.1]nonan-2-one (6), N-protonation is favored over O-protonation. In particular, in 5, N-protonation is favored by 100 kj mol ... 

There have been several previous ab initio molecular orbital studies of oxirane using the experimental geometry.30.3it34,35,38,39,63) These have been mostly concerned with ionization potentials and first order properties such as multipole moments. Some details are given in Table 10. As with aziridine, all the theoretical dipole moments except those calculated with the minimal Slater basis 33) are higher than the experimental value. 

This chapter represents an update to the previous two editions, published in 19771 and 19892, and covers the literature of the period 1989-1994 with some references to 1995 papers. It deals mainly with electrophilic additions across the C=C, C=Si and Si=Si bonds and includes both theoretical (ab initio calculations, orbital approach, molecular modelling etc.) and experimental aspects. Particular attention is paid to mechanistic studies, facial selectivity and neighbouring group participation. Synthetic utilization of electrophilic addition is discussed only if including substantial mechanistic insight purely synthetic work is not covered. Aside from the classical reactions, such as hydration, bromination etc., newly included material comprises aziridination (Section VI), attack at C=C bond by an electron-deficient carbon (Section VII) and those electrophilic reactions which utilize a transition or non-transition metal as the electrophile (Section VIII). 

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