RING structure-function relationships

The past 30 years have seen the development of a broad spectrum of widely applicable preparative methods for three- and four-membered carbocycles and the accumulation of detailed knowledge about their structure-reactivity relationships. Nowadays, more and more synthetic methodology is being developed, which utilizes the potential of small ring compounds as reactive entities. Cyclopropyl and cyclobutyl moieties in a molecule can be regarded as unique functional groups they allow transformations which are far more difficult or impossible with any of the more conventional functional groups. 

Model computational studies aimed at understanding structure-reactivity relationships and substituent effects on carbocation stability for aza-PAHs derivatives were performed by density functional theory (DFT). Comparisons were made with the biological activity data when available. Protonation of the epoxides and diol epoxides, and subsequent epoxide ring opening reactions were analyzed for several families of compounds. Bay-region carbocations were formed via the O-protonated epoxides in barrierless processes. Relative carbocation stabilities were determined in the gas phase and in water as solvent (by the PCM method). 

The structural theory of organic chemistry was developed in the last half of the nineteenth century. It led to the concept that chemical, physical and biological properties of all kinds must be a function of structural change. The earliest structure-property relationships (SPR) were qualitative. Examples are the directional effect of substituents on the benzene ring with respect to electrophilic aromatic substitution and orientation in... 

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