Thermal ene reaction of 4-(2-alkenylamino)-3-formyl-2(2H)-chromenones
摘要:
Intramolecular ene reaction of 4-(2-alkenylamino)-3-formyl-2(2H)-chromenones 7 involving carbonyl enophile proceeded stereoselectively to afford 5-hydroxychromen[3,4-b]-azepines 14. The intramolecular nucleophilic attack of hydroxy group to the enemine moiety in 14 gave 1,2-dihydro-2,4-ethanochromen[4,3-d][1,3]oxazin-5(4H,5H)-one derivatives 13 as final products. PM3 MO calculations of the process reveal that this ene reaction proceeds with two steps through an intermediate.
Synthesis of [1]Benzopyrano[4,3-b]pyrrol-4(1H)-ones from 4-Chloro-3-formylcoumarin
作者:Angel Alberola、Luis Calvo、Alfonso González-Ortega、Alfonso P. Encabo、M. Carmen Sañudo
DOI:10.1055/s-2001-17696
日期:——
2-Functionalized [1]benzopyrano[4,3-b]pyrrol-4(1H)-ones were obtained by the Fischer-Fink reaction starting from 4-chloro-3-formylcoumarin and different α-amino derivatives (e.g. glycinonitriles, ethyl glycinates and α-amino ketones). In general limitations to the synthetic method arise when α-amino derivatives with very reactive functions were used (e.g. carboxaldehyde groups or their acetal derivatives) leading to Knorr type reactions, or when they contain relatively inactive methylenes (e.g. carboxamide groups) which failed to complete the cyclization process.
Intramolecular ene reaction of 4-(2-alkenylamino)-3-formyl-2(2H)-chromenones 7 involving carbonyl enophile proceeded stereoselectively to afford 5-hydroxychromen[3,4-b]-azepines 14. The intramolecular nucleophilic attack of hydroxy group to the enemine moiety in 14 gave 1,2-dihydro-2,4-ethanochromen[4,3-d][1,3]oxazin-5(4H,5H)-one derivatives 13 as final products. PM3 MO calculations of the process reveal that this ene reaction proceeds with two steps through an intermediate.