7,7 -bis-indolizine

Bipyridinium ylides 133, generated in situ from 4,4-bipyridinium diquaternary salts 133, undergo 1,3-dipolar cycloaddition with activated alkynes under micro-waves, on KF-alumina in the absence of solvent, to give 7,7-bis-indolizines 134 in 81-93% yield (Scheme 9.40) [91]. The same reactions, when performed using benzene as a solvent under classical heating, yielded 7,7-bis-indolizine derivatives in yields of only 50-60% [92],... 

Keywords 4,4 -bipyridinium diquaternary salts, acetylenedicarboxylate, 1,3-di-polar cycloaddition, microwave irradiation, 7,7 -bis-indolizine... 

Dinica, R.M., Druta, I.I., and Rettinari, C. 2000. The synthesis of substituted 7,7 -bis-indolizines via 1,3-dipolar cycloaddition under microwave irradiation. Synlett, 1013-15. 

Biocatalysis could be employed to aid the formation of indolizine derivatives in an aqueous medium, as seen in Figure 16. Ultrasound activation was compared to conventional heating, affording 7,7 -bis-indolizines with similar yields in much shorter reaction times [31]. 

Theil, F. Sonnenschein, H. Kreher, T. Lipase-catalyzed resolution of 3,3 -bi-indolizines the first preparative access to enantiomerically pure samples. Tetrahedron Asymmetry 1996, 7, 3365-3370. 

Bis-[fluoren-<9-spiro-l >-1,2-diacetyl-5,8-dimethyl-1,8a-dihydro-indolizin-7-yl]- 2840 Bis-[fluoren-<9-spiro-l >-l, 2-dimethoxyearbonyl-1,8a-dihydro-indolizin-7-yl]- 2840 Bis-[fluoren-<9-spiro-l>-l,2-dimethoxycarbonyl-5.8-dimethyl-l,8a-dihydro-indolizin-7-yl]- 2840... 

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