Hybridisation rearrangements

Dienes, 11 addition to, 194-198 cisoid conformation, 197, 350 conjugated, 11 Cope rearrangement, 354 cycUsation, 346 cycloaddition to, 348 Diels-Alder reaction, 197, 349 excited state, 13 heat of hydrogenation, 16,194 isolated, 11 m.o.s of, 12 polymerisation, 323 Dienone intermediates, 356 Dienone/phenol rearrangement, 115 Dienophiles, 198, 350 Digonal hybridisation, 5 Dimedone, 202 Dimroth s Et parameter, 391 solvatochromic shifts, 391 solvent polarity, 391 Y and,392 Dinitrofluorobenzene proteins and, 172... 

Fig. 1. Quantitative restriction analysis for the evaluation of class switch recombination in polyclonally activated B cells. The rearrangement of the Syl region is reflected by the disappearance of the S7l germline restriction fragment (). This is measured by determination of the ratio of hybridisation intensities of Sr, and a reference probe. The loss of Sy, is calculated from the comparison of intensity ratios in lane A (liver DNA) and B (activated B cells). Further details are given in Section 4.3.1. of this chapter.

The a- vj y-equilibrium isotope effect observed in the Cope rearrangement of l,5-dimethyl-2-deuteriosemibullvalene [46] (Askani et al., 1982), in which a comparable exchange situation exists for deuterium bonded either to an sp -hybridised carbon or to a cyclopropane ring, also shows very good agreement with the observed values for the equilibrium constant and the thermodynamic parameter in cation [9]. 

The acid-catalysed rearrangement of thevinols has been shown to proceed with retention of configuration at C(7) and therefore not via an -hybridised centre at C(7) as had been previously proposed. A proposed mechanism for the rearrangement is shown in Scheme 100. Cathovaline-like compounds have been prepared from the rearrangement of vindoline derivatives in superacidic media,and the observed formation of the bridged 16-spiro compound (350) upon acetic anhydride-pyridine treatment of the hydroxyindolenine (349) represents a new rearrangement in iboga alkaloids see Scheme 101. 

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