Arenes cleavage

For the present discussion, a number of these conversions are of relevance. Phenolic dimeric model compounds of the 0-1, 0-0-4 and phenyl coumaran type are degraded via Ca-arene cleavage yielding methoxy-... 

It was found that the size of the phosphine ligand strongly determines the ROMP activity. If R in C3 is cyclohexyl, the much bulkier PCy3 ligand leads to lower temperatures of the arene cleavage, as measured by TGA. We also found that C3-type catalysts (with R=cyclohexyl and /-propyl) are very efficient initiators for the thermal, solvent-free polymerization of crude DCPD at temperatures above 80°C. This was unexpected, since, at that time, no ruthenium catalysts were known for the thermal polymerization of endo configurated DCPD. At R.T., solutions of C3 in DCPD are stable for weeks with almost no viscosity increase. 

The first use of chiral oxazolines as activating groups for nucleophilic additions to arenes was described by Meyers in 1984. " Reaction of naphthyloxazoline 3 with phenyllithium followed by alkylation of the resulting anion with iodomethane afforded dihydronaphthalene 10 in 99% yield as an 83 17 mixture of separable diastereomers. Reductive cleavage of 10 by sequential treatment with methyl fluorosulfonate, NaBKi, and aqueous oxalic acid afforded the corresponding enantiopure aldehyde 11 in 88% yield. 

Duffield and coworkers65 studied the El- induced mass spectra of five arene- (215-219) and four alkane sulfonylthioureas (220-223) and observed two rearrangement processes, namely loss of S02 from 215-219 and the elimination of ArS02 and RS02 with the thione sulfur atom from 215-223. The other fragmentations involved simple bond cleavages with and without hydrogen transfer (equation 48). The loss of H2S was evident for all the compounds studied except 221 and 222. It was, however, found to be a thermal and not an ionization process. 

Organometals and metal hydrides as electron donors in addition reactions 245 Oxidative cleavage of carbon-carbon and carbon-hydrogen bonds 253 Electron-transfer activation in cycloaddition reactions 264 Osmylation of arene donors 270... 

A short review of heterobond cleavage and sequential reactions of 1,2-thiazetidinones (P-sultams) has appeared <99PS193>. The first data for optically active P-sultams 33 have been reported. The precursor of 33 was the sulfonamide 32 which was obtained by use of a chiral tricarbonyl(r 6-arene)chromium(0) complex <99T14089>. 

Experimental values of bond dissociation enthalpies are scarce compared with the data available for standard enthalpies of formation. This is not surprising because most chemical reactions that have been studied thermochemically involve the cleavage and the formation of several bonds. The measured standard reaction enthalpies are thus enthalpy balances of various bond dissociation enthalpies, whose individual values are often unknown. Consider, for example, reaction 5.10, where the arene ring in (q6-bcnzene)chromium tricarbonyl is replaced by three carbonyl ligands. The enthalpy of this reaction at 298.15 K,... 

Triazenes are disguised diazonium ions which can be released under very mild acidic conditions. Inspired by the use of triazenes in natural product synthesis by Nicolaou et al. [127] and the pioneering work of Moore et al. [128, 129] and Tour et al. [130] in the synthesis of triazenes on a solid support and the final detachment to give iodoarenes, a whole set of triazene-based linkers has been developed (Tab. 3.10) [131]. The arene diazonium salts generated from the triazene linkers offer diverse opportunities for multifunctional cleavage. Two linkers based on tria-... 

Cleavage with fluoride other dialkylsilyl-linker are known [75-77, 102, 103, 191], for arenes... 

Cleavage with palladium/formate [194[, other linkers [195[ for arenes]... 

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