Diaryl-enynes

SCS-MP2 and the new perturbative B2-PLYP density functional methods provide accurate reaction barriers and outperform MP2 and B3-LYP methods when applied to the 1,3-dipolar cycloaddition reactions of ethylene and acetylene.39 Phosphepine has been shown to catalyse the asymmetric 3 + 2-cycloaddition of allenes with a variety of enones (e.g. chalcones) to produce highly functionalized cyclopentenes with good enantiomeric excess.40 The AuPPh3SbF6 complex catalysed the intramolecular 3 + 2- cycloaddition of unactivated arenyne- (or enyne)-yne functionalities under ambient conditions.41 A review of the use of Rh(I)-catalysed 3 + 2-cycloadditions of diaryl-and arylalkyl-cyclopropenones and aryl-, heteroaryl-, and dialkyl-substituted alkynes to synthesise cyclopentadienones for use in the synthesis of natural products, polymers, dendrimers, and antigen-presenting scaffolds has been presented.42... 

Coupling reactions. Cyclization of 1,6-enynes and diynes with concomitant aryl-coupling is realized using diaryl ketones (possessing a free o-CH). o-Acylarylrhodium hydride species are formed to initiate hydiometallation at the triple bond. 

Fused pyridines. 1-Ethynylcyclopentanol added dropwise with stirring to a mixture of acetyl chloride and a little ZnCl2 and POCI3 at 0° (exothermic to 35-40°), cooled to 20°, stirred for 1 h, and the mixture poured into 23% aq. NH4OH at 0° - 2-methyl-3,4-cyclopentenopyridine. Y 55% (85-93% with acetyl bromide or iodide). F.e.s. F.A. Selimov et al., Izv. Akad. Nauk SSSR Ser. Khim. 1988, 2604-7 2,4-dialkyl-, 2,3,4-trialkyl-, and 2,4-diaryl-pyridines (without POCI3), also 2,3,4,6-tetra-subst. pyridines from 1,3-enynes, s. ibid. 2600-4. 

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