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Mesomeric betaines dimerization

Thiopyran-3(6//)-ones (133 R=H or Me) are converted into 3-hydroxythiopyrylium perchlorates (134 R = H or Me) by triphenylmethyl perchlorate. Deprotonation of these salts (134) by tertiary base did not liberate the thiopyrylium-3-olates (132) but instead gave dimeric products (135 and 136) in high yield. Evidence for the transient formation of the mesomeric betaines (132) is provided by the appearance of a greenish-yellow coloration which rapidly fades. The parent betaine (132 R = H) gave exclusively the endo dimer (136 R = H) (70%). In addition to the endo dimer (136 R = Me) (75%), the 5-methyl derivative (132 R = Me) also gave a small amount of the exo dimer (135 R = Me) (6%). The dimerization (132 136) appears to be rapid and irreversible Attempts to trap the... [Pg.25]

See other pages where Mesomeric betaines dimerization is mentioned: [Pg.28]    [Pg.35]    [Pg.218]    [Pg.25]    [Pg.28]    [Pg.35]    [Pg.114]    [Pg.415]   
See also in sourсe #XX -- [ Pg.26 , Pg.92 ]



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