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16.17.1.2.1.1 Variation 1: Cyclization with Formic Acid

DOI: 10.1055/sos-SD-016-01192

Seela, F.; Ramzaeva, N.; Rosemeyer, H.Science of Synthesis, (200416967.

Although now largely superceded by trialkyl orthoformates for the preparation of 8-unsubstituted purines, formic acid still has a useful place in purine synthesis. Thus, cyclization of the uracil derivative 19 with formic acid under reflux conditions gives the 6-amino-5-(formylamino)uracil 20, which forms 1,3-diallylxanthine (21) upon heating in 10% aqueous sodium hydroxide (Scheme 20).[‌173‌] Similar conditions can be used for the reductive formylation of nitrosopyrimidines followed by ring closure with formamide, e.g. the direct synthesis of 23 from compound 22 (Scheme 20).[‌178‌]

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