A Convenient Synthesis of 3(2)-Trifluoroacetylaminobenzo[b]thiophenes and Thiophenes and Some of Their Iodo Derivatives

Abstract

Trifluomacetylamino derivatives 01 benzo[ hlthiophene and thiophene ( 3r-d) have been obtained by Cunius rearrangement ofthe comsponding acyl azides (la-d) with trifluomacetic acid. The iodination of these amide derivatives wilh iodine under mild conditions leads to iodinated products in excellent yield, except in the case of the 3-trifluomacetylaminobenw[ blthiophene (3a), which only gives a polymeric residue.As part of o w research program' directed toward the development of methodologies suitable for the preparation of polycyclic heteroaromatic compounds, we required a method to introduce iodine in the a-position to the amide group of a thiophene ring. Moreover, it is well known that the 3(2)-aminothiophene and 3(2)-aminoben-~[hlthiophene are labik2 A solution to this problem requires the direct generation of the amide functionality.We have previously described the preparation of the EL-butyl carbamates of thiophene and benzouthiophene by Cunius rearrangement of the corresponding acyl azides in m-butyl alcohol under reflux.3 and studied their halogenation3 and their reactivity as dianions toward bis-electrophilic reagents.1 Also we have shown that a Curtius rearrangement reaction can be used for the synthesis of 2-trifluoroacetylaminothiophene (3d).'We now report on the extension of this method to the preparation of 3(2)-trifluoroacetylaminobenzo[b]thiophenes (3a) and (3b), and 3-uifluoroacetylaminothiophene (3c). These amide derivatives of thiophene and benzo[Uthiophene and the corresponding iodinated products are potential starting materials to obtain thienoand benzoMthienoindole derivatives either ~ a SRNl process, as we have previously described for 3-amino-2-chl~ropyridine,~ ory& their reactivity as organodimetallic reagents as we have previously reported for the tert-butyl carbamate analogs and for the amide (3d).l -

On gonihedric loops and quantum gravity

“…The B matrix integration is in fact Gaussian so it can be integrated exactly. This integration was first presented in [18]. We first diagonalize the A matrix…”