title: A metal-free one-pot synthesis of benzo[c]chromen-6-ones from 3,4-dichlorocoumarins and butadienes using tandem photo-thermal-photo reactions.
abstract: An efficient, simple and versatile synthesis of biologically valuable benzo[c]chromen-6-ones is achieved using a tandem photo-thermal-photo reaction sequence starting from 3,4-dichlorocoumarins and a 1,3-butadiene. In this concise one-pot protocol, neither metal catalyst nor peroxide promoter is needed and the products can be purified through simple recrystallization in most cases. The synthesis consists of a reaction sequence of photo-induced [4 + 2] and [2 + 2] cycloadditions, silica gel promoted elimination of HCl and electrocyclic cyclobutene ring opening followed by a photo-induced 6π electrocyclization. The reactions proceed well with a range of dichlorocoumarins and some typical butadienes to provide the corresponding annulated products in 70-80% yield.
authors.affiliation: School of Chemistry and Chemical Engineering, Guangxi University, Nanning, Guangxi 530004, China. zhangminnju@hotmail.com.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Guangxi Environmental Monitoring Center, Nanning, Guangxi 530028, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Tian
authors.affiliation: School of Chemistry and Chemical Engineering, Guangxi University, Nanning, Guangxi 530004, China. zhangminnju@hotmail.com.
authors.forename: Pei
authors.initials: P
authors.lastname: Xiang
authors.affiliation: Guangxi Environmental Monitoring Center, Nanning, Guangxi 530028, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Huang
authors.affiliation: School of Chemistry and Chemical Engineering, Guangxi University, Nanning, Guangxi 530004, China. zhangminnju@hotmail.com.
authors.forename: Jianyi
authors.initials: J
authors.lastname: Wang
authors.affiliation: School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, Jiangsu 210093, China.
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Xu
authors.affiliation: School of Chemistry and Chemical Engineering, Guangxi University, Nanning, Guangxi 530004, China. zhangminnju@hotmail.com.
authors.forename: Min
authors.identifier: http://orcid.org/0000-0002-2458-9564
authors.initials: M
authors.lastname: Zhang
mesh_terms: D001578:Benzopyrans / Q000138:chemical synthesis* / Q000737:chemistry*; D002070:Butadienes / Q000737:chemistry*; D060326:Chemistry Techniques, Synthetic; D003374:Coumarins / Q000737:chemistry*; D049934:Isocoumarins; D055668:Photochemical Processes; D013696:Temperature
chemical_list: C000596410:6H-benzo(c)chromen-6-one; D001578:Benzopyrans; D002070:Butadienes; D003374:Coumarins; D049934:Isocoumarins; C046235:3,4-dichloroisocoumarin; C031763:1,3-butadiene