Journal of Organic Chemistry p. 2826 - 2837 (1991)
Update date:2022-08-04
Topics:
Kozikowski, Alan P.
Tueckmantel, Werner
A short and efficient synthesis of the title compounds is described, starting from readily available α,β-unsaturated carbonyl compounds 5 and β,γ-unsaturated ketones 4.Their directed aldol condensation yields the unsaturated hydroxy ketones 6 which are dehydrated to the trienones 7.Although these fail to cyclize on heating, the intramolecular Diels-Alder reaction can be brought about after reduction or alkyllithium addition to the carbonyl group.Alkyl substitution in the positions 1,2,3,5, and 7 has little influence on the ease and yield of cyclization, whereas a methyl group at C-4 hinders it considerably.The title compounds are obtained as mixtures of usually all four stereoisomers, of which one predominates (>/- 50percent) in most cases.O-Alkylation in 8b has little effect on the isomer distribution.The major isomer of the 6-bromo derivative forms a highly crystalline p-nitrobenzoate 27, which permits stereochemical assignment through X-ray crystallography; for most other products assignments can be made by comparison and further evaluation of their 1H NMR spectra.The results are discussed in terms of a simple transition state model.The intramolecular Diels-Alder reaction fails when the length of the tethering chain is reduced by one, or when the diene unit becomes part of a furan ring.Trienones 7 are sensitive to autoxidation, of which some products are described.
View MoreQingdao Pana-Life Biochem Co.,Ltd.
Contact:86-532-87683902
Address:No.967 Dalao Road, Licang Zone, Qingdao City,Shandong, China 266021
Henan PURUI Pharmaceutical Co., Ltd.
website:http://www.puruipharm.com
Contact:17739583555
Address:Yezhuangqiao,Xihua town, Henan province
Shijiazhuang Frontierchem Co., Ltd.
Contact:+86-311-89271196
Address:4-4-202 No.15 Biandian Street,Shijiazhuang
Contact:+49-4101-3053-0
Address:Waldhofstrasse 14 ,25474 Ellerbek Germany
Hubei Onward Bio-Development Co., Ltd.
Contact:+86-718-8417012
Address:No.517,Shizhou Avenue,Enshi City,Hubei Province,China,445002
Doi:10.3987/COM-11-12206
(2011)Doi:10.1021/jp206930v
(2011)Doi:10.1021/ja206022p
(2011)Doi:10.1002/mrc.1260310509
(1993)Doi:10.1007/BF00472477
(1990)Doi:10.1016/j.tet.2011.07.080
(2011)