Cyclohexane derivatives double activation

Busson and van Beylen [205] studied the role of the cation and of the carbanionic part of the active centre during anionic polymerization in non polar media. They were interested in the problem of complex formation between the cation and the monomer double bond [206] and they therefore measured the reaction of various 1,1-diphenylethylenes with Li+, K+ and Cs+ salts of living polystyrene in benzene and cyclohexane at 297 K. Diphenylethy-lene derivatives were selected for two reasons. 

More recently, Enders et al. disclosed a facile access to tetracyclic double annulated indole derivatives 175, which basically relies on the chemistry of the acidic 2-substituted indole and its nitrogen nucleophilicity. Indeed, the employed quadruple cascade is initiated by the asymmetric aza-Michael-type A-alkylation of indole-2-methylene malono-nitrile derivative 174 to o,p-unsaturated aldehydes 95 under iminium activation (Scheme 2.57). The next weU-known enamine-iminium-enamine sequence, which practically is realized with an intramolecular Michael addition followed by a further intermolecular Michael and aldol reactions, gives access to the titled tetracyclic indole scaffold 175 with A-fused 5-membered rings annulated to cyclohexanes in both diastereo- and enantioselectivity [83]. 

The study of exothermic gas phase reactions of laser descried Ln ions with various hydrocarbons with Fourier transform mass spectrometry has shown that the single and double dehydrogenations and the formation of the corresponding LnR cation species takes place in all cases [50-53]. The reactions of Sc , T", La and Gd" with cyclohexane and cyclohexene to produce the benzene derivatives Ln (QH5), which account for more than 99% of the total product distribution [51, 53]. The reaction of the scandium primary product ion Sc CQH ) with cyclohexene gives the bis(benzene)-scandium ion. Pr" and Eu" indicate lower activity than Gd " and Sc " in reactions with alkanes [51]. 

---