Regioselective Aryl Radical Cyclization: Access to Pyrimidine-Annelated <i>Spiro</i> Heterocycles Through <i>5-exo</i> Ring Closure
作者:K. Majumdar、P. Mukhopadhyay
DOI:10.1055/s-2004-829133
日期:——
Aryl radical cyclization of a range of 6-(2'-bromophenoxymethyl)-1,3-dimethyluracils 4a-g was carried out with tributyltin chloride and sodium cyanoborohydride in the presence of AIBN for four hours to give exclusively the '5-exo' cyclization products, 1,3-dimethylspiro[pyrimidine-6,3'-2',3'-tetrahydrobenzofuran]-2,4-diones 5a-g in 92-95% yield. The starting materials were in turn prepared in 90-92%
在 AIBN 存在下,用三丁基氯化锡和氰基硼氢化钠对一系列 6-(2'-溴苯氧基甲基)-1,3-二甲基尿嘧啶 4a-g 进行芳基环化 4 小时,仅得到 '5-exo'环化产物,1,3-二甲基螺[嘧啶-6,3'-2',3'-四氢苯并呋喃]-2,4-二酮5a-g,收率92-95%。通过在丙酮中在无水碳酸钾存在下将6-氯甲基-1,3-二甲基尿嘧啶与各种2-溴苯酚或2-溴萘酚回流8小时,进而以90-92%的产率制备起始材料。