Synthesis of Substituted Imidazo[1,2-<i>h</i>][1,7]naphthyridines as H<sup>+</sup>/K<sup>+</sup>-ATPase Inhibiting Drug Precursors via Directed<i>ortho</i>-Metalation of Imidazo[1,2-<i>a</i>]pyridines
作者:Jörg Senn-Bilfinger、Bernhard Kohl、Georg Rainer、Wilm Buhr、Hans Holst、Peter Zimmermann
DOI:10.1055/s-2008-1067264
日期:2008.10
Selective directed ortho-metalation (DOM) of 2,3-dimethyl-8-(pivaloylamino)imidazo[1,2-a]pyridine in the 7-position was achieved with tert-butyllithium. Subsequent reaction of the lithiated derivative with tributylchlorostannane to the corresponding 7-trialkylstannyl analogue and palladium-catalyzed Stille acylation with 3-arylpropenoic acid chlorides in the presence of lithium chloride gave the corresponding 7-acylated imidazopyridines in good yields. Cyclization to the target imidazonaphthyridines, which are precursors in the synthesis of gastric H+/K+-ATPase inhibiting drugs, was achieved by treatment with strong acid. For scaled-up production of 2,3-dimethyl-9-phenyl-9,10-dihydroimidazo[1,2-h][1,7]naphthyridin-7(8H)-one, a tin-free process has been developed. Accordingly, the 7-lithiated 2,3-dimethyl-8-(pivaloylamino)imidazo[1,2-a]pyridine was reacted directly with cinnamaldehyde and the resultant alcohol oxidized with manganese dioxide to give the unsaturated 7-acylated imidazopyridine.
用叔丁基锂实现了 2,3-二甲基-8-(新戊酰氨基)咪唑并[1,2-a]吡啶 7 位的选择性定向正金属化 (DOM)。随后,锂化衍生物与三丁基氯化锡反应生成相应的 7-三烷基锡类似物,并在氯化锂存在下与 3-芳基丙烯酸氯化物进行钯催化的斯蒂尔酰化反应,以良好的收率得到相应的 7-酰化咪唑并吡啶。通过强酸处理,环化生成了目标咪唑并萘啶类化合物,它们是合成胃 H+/K+-ATP 酶抑制药物的前体。为了扩大 2,3-二甲基-9-苯基-9,10-二氢咪唑并[1,2-h][1,7]萘啶-7(8H)-酮的生产规模,开发了一种无锡工艺。因此,7-硫代 2,3-二甲基-8-(新戊酰氨基)咪唑并[1,2-a]吡啶直接与肉桂醛反应,生成的醇与二氧化锰氧化,得到不饱和的 7-酰化咪唑吡啶。