Fragmentation of 2,2,2-triphenylethoxychlorocarbene: evidence for ultrafast fragmentation-rearrangement in excited diazirines.
[reaction: see text] Photolysis of 3-(2,2,2-triphenylethoxy)-3-chlorodiazirine gives 2,2,2-triphenylethoxychlorocarbene which fragments with 1,2-phenyl migration and loss of CO and Cl(-) to yield the 1,1,2-triphenylethyl cation and thence 1,1,2-triphenylethene by proton loss. However, ps and fs laser flash photolysis provides evidence that up to 25% of the alkene product stems from carbocation that arises directly from excited diazirine rather than from the carbene.
Diaziridines and Diazirines
Diazirines and diaziridines are three-membered heterocycles containing two nitrogen atoms. Photolysis or thermolysis of diazirines generates carbenes; consequently, diazirines are frequently applied as easily handled and readily synthesized carbene progenitors. In this role, diazirines have been widely employed in biological systems as photoaffinity probes and as carbene precursors in surface modification research. Diaziridines have been used synthetically as aziridinating reagents and several diaziridines possess interesting biological activity. This chapter reviews developments in diazirine and diaziridine chemistry over the period 1996–2007 and encompasses modern ab initio theoretical studies, the application of various experimental methods to structural analysis, thermodynamic aspects, reactivity with and without ring cleavage, contemporary synthesis, and applications.
Evidence of spurious results along with spatially autocorrelated errors in the context of geographically weighted regression for two independent SAR(1) processes
AbstractThe aim of this paper is to examine the performance of the geographically weighted regression (GWR) technique in terms of recognizing linear relationships at the local level. Using a Monte Carlo analysis with two independent spatially autocorrelated SAR(1) processes, this study finds that spurious behavior exists at the local level along with spatially autocorrelated errors. Therefore, GWR estimation results must be interpreted with caution.
