1- PHENYL 1,4-PENTADIYNE

A derivative of the oxo form of a 3-hydroxyselenophene has been obtained by a quite different route.123 1,5-Diphenyl-1,4-pentadiyn-3-one (94) adds hydrogen selenide and gives a mixture of 2,6-diphenyl-1-seleno-y-pyrone (95) and 2-benzylidene-3-oxo-5-phenyl-2,3-dihydroselenophene (96). 

Phenylmercuric acetate, with methallyl alcohol to yield 2-methyl-3-phenylpropion-aldehyde, 51, 17 1-PHENYL-1,3-PENTADIYNE, 50,... 

Phenyl isocyanate, with ethyl hydrazine-carboxylate to give 4-phenyl-l-car-bethoxysemicarbazide,51,122 Phenylmercuric acetate, with methallyl alcohol to yield 2-methyl-3-phenyl-propionaldehyde, 51, 17 1-PHENYL-1,3-PENTADIYNE, 50, 97 1-PHENYL-1,4-PENTADIYNE. 50, 97 a-Phenylpentanal, from 2-benzyl-4,4,6-trimethyl-5,6-dihydro-l,3(4H)-... 

The cycloaddition of phenylarsine or a trimethylsilylphenylarsine to a pentadiyn-3-one (Scheme 6) leads to a 1 -phenyl-2-arsolen-4-one of type (24). This reacts with diphenylketene to give the diphenylmethylene analogues (25) which are intermediates in the synthesis of the benz[/]arsindoles (26) (76T2131). 

When l-phenyl-5R-3-oxo-l,4-pentadiynes were used as starting materials, 4-oxo-4/7-tellurins with different substituents in the 2- or 6-positions were obtained7 ... 

Phenyl -1,3-pentadiyne. A flask containing a magnetic stirrer and a solution of 2 g. of sodium hydroxide in 50 ml. of... 

Phenyl-1,3-pentadiyne has been prepared by the dehydro-bromination of the corresponding butadiene tetrabromide.6 Other unsymmetrical 1,3-diynes have been prepared by scheme... 

Very high reactivity toward thiol addition is observed when the diyne system is attached ro a carbonyl group, but the stereoselectivity drops sharply, and mixtures of cis-trans isomers are obtained irrespective of solvent. Thus, the product from the addition of methanethiol to l-phenyl-2,4-pentadiyn-l-one (114) in either methanol or THE consists of the cis (115) and trans (116) isomers with the former predominat-ing s- . It was shown that 116 does not arise by isomerization of 115. Similarly, addition to 2,4-hexadiynoic acid (117) in DMSO yields a mixture of cis-trans isomers (118) . ... 

Addition of amines to carbonyl-activated diynes occurs with great ease, and often the initial adducts react further to give cyclic products. Syn addition occurs in the reaction of piperidine with l-phenyl-2,4-pentadiyne-l-one (151) in either ethanol or ether as solvent giving 152... 

Attachment of two alkynyl groups to a CHj group confers an unusually high acidity on the protons, and as a consequence 1,4-diynes undergo basc-catalysed rearrangement under very mild conditions. Thus, l-phenyl-l,4-pentadiyne (269) gives l-phenyl-l,3-pentadiyne (271) in good yield upon treatment with ethanolic... 

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