Pleiadene, dimerization

Irradiation of the sulfone (39) in benzene gave, not the strained cyclobutene derivative, but the pleiadene dimer (40).39... 

In the next step, pleiadene dimerizes. Synthesis of either ( )-3,5-dimethoxystil-benes or 3,5-dimethoxydibenzyls was carried out by selective removal of the 4-methoxy group of 3,4,5-trimethoxystilbenes I (Ri = MeO Ar = Ph, 2-MeOCfiH4, 3-MeOC6H4, 4-MeOC6H4, 3,4,5-(MeO)3C6H2) [75]. The reaction was performed under electron transfer conditions with Na metal in THE. It was shown that 4, 4"-diethylstilbestrol quinone reacted with nucleosides, nucleotides, and amines... 

The new chiral a A, -phosphenium cations (190) undergo chelotropic cycloaddition with buta-1,3-diene to produce a cr-cycloadduct (191) (Scheme 74). The 4-1-4-cyclodimerization of 2,3-dihydroisoquinolines yields 3,7-diazatricyclo[4.2.2.2 ] dodeca-9,ll-dienes. ° Inter- and intra-molecular 4 - - 4-cycloadditions of 2-pyridones have been used in synthetic approaches to natural products such as fiisicoccin A and taxol (paclitaxel). The dimerization of pleiadene is not anh-speciflc as previously thought but yields a mixture of syn- and anft-dimers. ... 

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