The synthesis of thieno[3,2-b]pyrrole (VI) was carried out by conversion of 3-nitro-2-inethylthiophene t o 3-nitro-2thenaldehyde followed by application of the azlactone synthesis t o give 3-nitro-2-thienylpyruvic acid, which was reduced t o the thienopyrrolecarboxylic acid (V). Decarboxylation of V t o thieno[3,2-b]pyrrole (VI) was effected by heat in an evacuated sealed tube. A similar reaction scheme proceeding from 2-nitro-3-methylthiophene mas examined in order t o obtain the isomeric thienopyrrole, but the final step, reduction of the pyruvic acid, was unsuccessful.
The course of ring opening of ethyl and phenyl glycidyl ethers has been studied with such representative nucleophilic reagents as ethyl malonate, ethyl ethylmalonate, ethyl cyanoacetate and ethyl acetoacetate using molar equivalents of base. In all cases, ring opening was found to occur at the primary carbon atoms to give a series of «-substituted--valerolactones.Although the literature contains frequent references to the addition to alkene oxides of such nucleophilic reagents as the respective anions of malonic ester,1-9 substituted malonic esters,7,8 acetoacetic ester9-12 and cyanoacetic ester,13 there is only one reference14 to the addition of nucleophilic reagents (malonic ester) to glycidyl ethers. The purpose of this paper is to report on a study of the chemical reactivity of this interesting class of compounds in relation to their condensation with representative nucleophilic reagents. Furthermore, in the light of present interest in the direction of ring opening in Sn2 attack on unsymmetrical epoxides, we have observed that in the case of the glycidyl ethers studied the attack by the nucleophilic reagent occurs preferentially at the unsubstituted or primary carbon of the terminal epoxides. Recent evidence9 would indicate that in the condensation of phenyl glycidyl ether with the ethyl cyanoacetate or ethyl acetoacetate anion, ring opening might conceivably take place in either direction. However, we were unable to demonstrate attack at the secondary carbon in detectable amounts. This is in accord with all presently held theoretical considerations.The recent study by Adams and VanderWerf9 of the base-catalyzed condensation of acetoacetic ester with unsymmetrical epoxides has indicated that, in this case at least, the allylic resonance of such epoxides as styrene oxide and 3,4-epoxy-l-butene may have the effect of lowering the energy of the transition state involved in nucleophilic attack at the secondary carbon atom. In the case of 3,4epoxy-l-butene, attack took place at both the primary and secondary carbons, apparently with equal ease. This was interpreted as evidence that the effect of the allylic resonance outweighed the steric factors which would favor attack at the primary carbon.(1) (a) W.
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