Aldehydes alkyne-carbonyl metathesis

We found SbFs in the presence of alcohol-catalyzed alkyne-carbonyl metathesis of substituted phenylalkyne with aldehyde, and it was extended to the cascade reaction combined with the Nazarov cyclization of the formed alkenyl phenyl ketones such as 305 (Scheme 24.75). " In this sequence, an appropriate choice of alcoholic additive is critical for the efficient formation of indanone 306. A combination of intramolecular alkyne-carbonyl metathesis with Nazarov cyclization has been independently reported for the construction of polycyclic enone by Yamamoto et al. "... 

SCHEME 24.74. Alkyne-carbonyl metathesis of 1-phenyl-1-propyne and aldehydes. 

In sharp contrast to the stabihty of cationic vinylidene complexes towards air, neutral vinylidene complexes of the type TpRuClf = C = CHR)(PR3) convert readily into the corresponding carbonyl compounds TpRuCl(CO)(PR3) and the aldehyde RCH = O in solution. This process was intensively studied by Bianchini et al. using a similar precursor. In addition, neutral vinylidene complexes are substitutionally labile. Thus, the vinylidene moiety is easily replaced by L (L = py, PMe3, CO). In fact, even metathesis with other terminal alkynes (added in excess) is feasible. ... 

Progress in rhenium chemistry reported in 1991 is reviewed.549 There is much important material in a review of methyltrioxorhenium catalysed alkene metathesis, oxidation and aldehyde alkenation, a review of the insertion of activated alkynes into the metal-metal bond of dinuclear manganese and rhenium carbonyl complexes. i a review of the reactions of [Cp(CO)2Mn=CPh]+ towards electron rich alkynes and nitriles552 and a review of the discovery of tRe(CBu )(CHBu ) OCMe(CF3)2 2l and recent results covering the metathesis of alkenes. s... 

Stereodefined alkenes are ubiquitous structural motifs in many natural products and pharmaceutics, and, moreover, they serve as a foundation for a broad range of chemical transformations. Nowadays, carbonyl olefination, elimination, alkyne addition, alkenylation, and alkene metathesis constitute the most widely used methods for the stereoselective synthesis of various alkenes [1-3]. Whereas no single method provides a universal solution to stereoselective alkene synthesis, the olefination reactions of aldehydes and ketones with phosphorus-stabilized carbon nucleophiles have enjoyed widespread prominence and recognition owing to their simplicity, convenience, complete positional selectivity, and generally high levels of geometrical control [4-9]. 

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