Substitued acids 1,4-pentadiene

Diethoxyphosphoryloxy)-1,3-butadiene and 2-(diethoxyphosphoryloxy)-1,3-pentadiene are good dienes and are compatible with Lewis acid catalysts.50 They exhibit the regioselectivity expected for a donor substituent and show a preference for endo addition with enones. 

The combination of cis-trans isomerism with iso-syndio and erythro-threo dispositions gives complex stractures as exemplified by the 1,4 polymers of 1-or 4-monosubstituted butadienes, such as 1,3-pentadiene (72, 73), and 2,4-pentadienoic acid (74, 75) and of 1,4-disubstituted butadienes, for example, sorbic acid (76). This last example is described in 32-35 (Scheme 6, rotated Fischer projection). Due to the presence of three elements of stereoisomerism for each monomer unit (two tertiary carbons and the double bond) these polymers have been classed as tritactic. Ignoring optical antipodes, eight stereoregular 1,4 structures are possible, four cis-tactic and four trans-tactic. In each series (cis, trans) we have two diisotactic and two disyndiotactic polymers characterized by the terms erythro and threo in accordance with the preceding explanation. It should be noted that here the erythro-threo relationship refers to adjacent substituents that belong to two successive monomer units. 

In a series of papers on the photochemical synthesis of cyclo-pentadiene and pyrrole derivatives, Siis and Moller reported the preparation of indoles which could not be made by the Fischer method. Primarily, these were indoles with electron-withdrawing substituents in the benzene ring. Included was the synthesis of 4-azaindole-3-carboxylic acid (18, Scheme 2). The reaction was extended to the synthesis of the other three azaindoles. ... 

This phosphinazine is thermally stable [71], It is converted into cyclopentadienone hydrazone on acid hydrolysis [73] Diazocyclo-pentadiene also couples with dialkyl phosphites [59], A variety of substituted dlazocyclopentadienes also react with triphenylphosphine to.give phosphinazines [63,82] but if there are alkyl or aryl substituents at both the 2- and 5-positions no phosphinazine is formed [82]. 

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