Carboxylic acids, acetylenic cleavage

Nickel peroxide is a solid, insoluble oxidant prepared by reaction of nickel (II) salts with hypochlorite or ozone in aqueous alkaline solution. This reagent when used in nonpolar medium is similar to, but more reactive than, activated manganese dioxide in selectively oxidizing allylic or acetylenic alcohols. It also reacts rapidly with amines, phenols, hydrazones and sulfides so that selective oxidation of allylic alcohols in the presence of these functionalities may not be possible. In basic media the oxidizing power of nickel peroxide is increased and saturated primary alcohols can be oxidized directly to carboxylic acids. In the presence of ammonia at —20°, primary allylic alcohols give amides while at elevated temperatures nitriles are formed. At elevated temperatures efficient cleavage of a-glycols, a-ketols... 

The monomer in (12.30) was made from glycerol, acetone, and acetylene. The alternating copolymer with maleic anhydride cross-links on standing in a moist atmosphere.156 (The carboxylic acid that results from the action of water on the anhydride catalyzes the cleavage of the ac-... 

Oxidative cleavage of acetylenes RC=CH (R = Ph, Bu, hexyl, heptyl, cyclopentyl or PhCH2CH2) with bis[trifluoroacetoxy)iodo]pentafluorobenzene in wet benzene gives carboxylic acids RC02H. Alkynes 263 (R, R = H, Me, Et, Pr, Bu or Ph) undergo an oxidative rearrangement by the action of [hydroxy(tosyloxy)iodo] benzene in methanol to yield the esters 264. ... 

The literature contains very little information about the mass spectra of furan compounds substituted with an unsaturated chain. The fragmentation mode of some 2-styryl- and 2,5-di-styrylfuran derivatives has been studied <920MS(27)615>. Each styryl substituent has an a-carboxylic acid or methyl carboxylate substituent. The molecular ion is the base peak for styryl and distyryl derivatives and the distyryl species show less fragmentation than the styryl species. An important fragmentation pathway for both these derivatives, in addition to simple bond cleavage, is the loss of formic acid or methyl formate, presumably forming acetylenic fragments (Schemes 1 and 2). 

Pentafluorophenyl iodosotrifluoroacetate Carboxylic acids from acetylene derivs. Oxidative cleavage under mild conditions... 

As corroborated by deuterium labeling studies, the catalytic mechanism likely involves oxidative dimerization of acetylene to form a rhodacyclopen-tadiene [113] followed by carbonyl insertion [114,115]. Protonolytic cleavage of the resulting oxarhodacycloheptadiene by the Bronsted acid co-catalyst gives rise to a vinyl rhodium carboxylate, which upon hydrogenolysis through a six-centered transition structure and subsequent C - H reductive elimina-... 

In Chart 1 are listed the most frequently employed mono-donor building blocks in SPOS such as tertiary amines, phosphines, phosphites, alcohols, boronic acids, stannanes, acetylenes, carboxylates and various organometallic nucleophiles. These building blocks are mostly used for the diversification steps to decorate the previously constructed core structures (see Figures 1.9.1 and 1.9.2) or for the final cleavage reactions. 

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