反应详情

The 2-chloro-5-aminopyridine A is converted by heating in the presence of ester B and triethyl orthoformate to the condensation product C as a mixture of olefin isomers (Scheme 1). Various esters that are commercially available, known in the literature or prepared using known literature procedures are applicable to the reaction. Intermediate C is added to hot Dowtherm™ A to facilitate the ring closure and to afford the 1,5-naphthyridine D. Treatment of D with phosphorus oxychloride affords the key intermediate E (Scheme 1).

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