Indolizines, from quinolizines

Enantiomerically pure triene 395, whose chirality stems from that of /3-D-ribofuranosc, was transformed into the chiral pyrrolidine 396 by intramolecular iodoamination. A subsequent RCM reaction gave indolizine derivative 397. Treatment of this compound with nucleophiles afforded mixtures of indolizine and quinolizine derivatives in... 

A novel rearrangement of suitably 2-substituted side-chain perhy-dro-isoxazolo[2,3-a]pyridines has been shown to afford indolizine and quinolizine derivatives (86TL1727). Thus, 2-spirocyclopropylperhydro-isoxazolo[2,3-a]pyridine (61), obtained as a mixture with the 3-spiro isomer from the reaction between 3,4,5,6-tetrahydropyridine-l-oxide and methylene cyclopropane, undergoes thermal rearrangement (400°C, 0.2 mmHg) to the quinolizidin-2-one (62). 

The addition of the phthalimido anion to triesters of 2-phosphonopropenoic acid at room temperature gives an initial adduct, which is unexpectedly inert to benzaldehyde reaction but which adds to a second molecule of the phosphonic diester to form a second carbanion the latter undergoes an intramolecular WEH condensation to give the heterocyclic system 371 indolizine and quinolizine phosphonic diesters have been similarly obtained from maleimide, succinimide and glutarimide anions ". The ability of piperidine to add to the compounds 372 decreases in the order R R = (BuO)H (exothermic reaction) > (BuO)2 > (BuO)Me > Bu2 (the last requires heat) ". Ethenylphosphonic diamides (372 R = r2 = NR2) are unreactive to nucleophiles (by virtue of reduced electrophilic character at phosphorus and thus reduced electron attraction from the carbon-carbon double bond) but are reactive to electrophilic reagents. ... 

In methanol, isoquinoline and the ester gave the benzo[fif]indolizine [(121), cf. Section II,D,3] while in ether the labile adduct, tetra-methyl llbH-benzo[a]quinolizine-l,2,3,4-tetracarboxylate (122) was obtained. The labile adduct is much less easily isoraerized than the 9-methyl-9aH-quinolizines derived from pyridines (Section III,F,1) but with boiling xylene or, better, with sulfuric-acetic acids the cor-... 

Thus, the main products from quinaldine in aprotic solvent acetonitrile are quinolizine 280 and indolizine 281a (rather than pyridoazepine 282) in protic solvent methanol only indolizine 281a forms, but in both cases higher-fused products (1 3 and 1 4 adducts) are accompanying. Also the long-lasting discussion about the products obtained from 6-bromoquinaldine has been settled in favor of the two isomers 283 (76J(P1)692). 

From the reaction of pyridine with DMAD in methanol the indolizines (157) and (158) have been obtained, but 69% of the quinolizine (159) is formed on reaction in ether. 

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