Preparation of New Nitrogen-bridged Heterocycles. 50.1 Syntheses of Some Heterocyclic Compounds Starting from Pyridinium 1-(Ethoxycarbonylacetyl)methylides
The reactions of the title methylides with dialkyl acetylenedicarboxylates gave the corresponding 3-(ethoxycarbonylacetyl)-indolizine derivatives, whose 3-substituent was smoothly converted to a coumarin skeleton by Knoevenagel reaction with salicylaldehyde. The reactions of the methylides with carbon disulfide and alkylating agent in the presence of a base afforded pyridinium 1-[alkylthio(thiocarbonyl)](ethoxycarbonylacetyl)methylides, and the S-alkylations of these ylides with phenacyl bromides and subsequent alkaline treatment of the resulting pyridinium salts gave ethyl 3-alkylthio-1-(arylcarbonyl)thieno[3,4-b]indolizine-9-carboxylates.
Syntheses of Some 1-(α-Hydroxybenzyl)thieno[3,4-b]indolizine Derivatives and Their Unexpected Condensation Reactions
Some ethyl 3-(benzyl or methylthio)-1-(alpha-hydroxybenzyl)- thieno[3,4-b]indolizine-9-carboxylates were prepared by the reduction of the corresponding 1-benzoyl derivatives with sodium borohydride. These compounds were considerably unstable and their treatment with acetic acid afforded the unexpected condensation products.