The chemical development of CI-972 and CI-1000: A continuous nitration, a MgCl2/Et3N-mediated C-alkylation of a chloronitropyrimidine, a catalytic protodediazotizatlon of a diazonium salt, and an air oxidation of an amine

Article abstract of DOI:10.1021/op000298d

Efficient, large-scale processes were developed for the preparation of the potent PNP inhibitors 2,6-diamino-3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2-d]pyrimidin-4-one hydrochloride, monohydrate (1) and 2-amino-3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2-d]pyrimidin-4-one hydrochloride, monohydrate (2). We report (1) a safe, continuous nitration process for the preparation of 2-amino-6-chloro-5-nitro-4-pyrimidinol (8a) and its stable diisopropylamine salt (8b), (2) the first MgCl₂/ Et₃N-mediated C-alkylation of a chloronitropyrimidine, (3) a rare catalytic protodediazotization of the diazonium salt 2-amino-4-oxo-7-thiophen-3-ylmethyl-4,5-dihydro-3H-pyrrolo[3,2-d]pyrimidine-6- diazonium chloride (14), (4) a single-step process to prepare 2 directly from 2-amino-6-hydroxy-5-nitro-a-(3-thienylmethyl)-4-pyrimidineacetonitrile (12) using a sponge nickel-catalyzed reduction, and (5) a method to convert the over-reduction by-product 2,5-diamino-6-(1-aminomethyl-2-thiophen-3-yl-ethyl)-pyrimidin-4-ol (16) into 2 using air oxidation.