ChemInform Abstract: Synthesis of 7‐Unsubstituted 7H‐Pyrrolo(2,3‐d)pyrimidines.

Abstract

224ChemInform Abstract As exemplified in the scheme for (VII) and (VIII), 7-substituted pyrrolopyrimidines can be prepared from (I) via (IV) by a previously published procedure. The desired removal of the substituent is accomplished in most instances by heating in PPA; thus, the substrates (VIII), (VIIb), (VIIc), (VIIe) and (XIa) are converted to the title compounds (IX) and (XIb) (only one yield given for products suchas (IX), obtained from a number of different starting materials). In contrast to (VIIa), undergoing degradation to give (X), the thio analogue (XIIa) affords the target compound (IXa). The cycloalkyl-substituted systems (XIIb) and (XIIc) both yield (IXb) on heating in phosphoric acid, whereas (XIId) and (XIIe) fail to give the corresponding products (dehydration to styrene derivatives occurs in t he case of (XIId); yields of 83-93%). Monoacyl derivatives of (VII), (VIIIa) and (XIIa) are transformed to the free amines (e.g. (XIIIa)/(XIIIb) → (VIIIa)); a different behaviour, however, is displayed by the analogous diacyl compounds. While (XIIIc) and (XIIId) again afford (IXa), the reactions of (XIV) and, similarly, of (XVI) proceed with migration of an acyl group to give (XV) and (XVII).