Alcohols naphthyridine-derived

Tryptamine, tryptophan and their derivatives are widely used in the synthesis of indolo[3,2,l-naphthyridine derivatives. Thus, refluxing tryptamine 35 with 2-formylbenzoic acid 36 in alcohol followed by the addition of concentrated hydrochloric acid afforded hexahydrobenzo[/z]indolo[3,2,l-[Pg.194]

The cyclic enaminone 566 reacts with acetylenic esters followed by heating in alcohols to give the hexahydroimidazo[l,2,3-y][l,8]naphthyridine derivatives 567 in good yields. When the enaminone 566 is mixed with the allene diester shown at room temperature for 72 hours, the hexahydro-imidazonaphthyridine 568 is obtained. Scheme 153 (93S111). 

Queguiner and his group used lithiated pivaloylaminopyridines 407 with aldehydes to synthesize amino ketones. Oxidation of alcohols 408 with CrOs or Mn02 leads to o-aminop)uidyl ketones 409 (Scheme 91). Amides 409 are hydrolyzed to the amines 410 with HCl. Both 409 and 410 were successfully utilized in Friedlander condensations with various ketones that produced naphthyridine derivatives (89JHC105). 

Solid-phase syntheses have become increasingly popular during the period of this review, with examples including the synthesis of 5,6,7,8-tetrahydro[l,6]naphthyridines from Meldrum s acids derived from /3-amino alcohols via Hantzsch condensation and cyclization with cyclative cleavage from the resin (using 70% trifluoroacetic acid (TFA)/dichloromethane (DCM) followed by 5% triethylamine/DCM) <1999S1951> and also of isoquinolinones and 5-oxo-5,6-dihydro-[l,6]naphthyridines <1995JOC5748>. 

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