Cyclopentene Synthesis from 1,3-Dienes via Base-Induced Ring Contraction of 3,6-Dihydro-2H-thiopyrans: Studies on Diastereoselection and Mechanism
- 1 January 1996
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Organic Chemistry
- Vol. 61 (14), 4725-4738
- https://doi.org/10.1021/jo960537o
Abstract
An investigation of the scope and mechanism of a new synthesis of cyclopentenes from 3,6-dihydro-2H-thiopyrans is described. Alkyl halides substituted with an electron-withdrawing group in the α-position were reacted with sodium thiosulfate, yielding the corresponding Bunte salts, which could be transformed to reactive thiocarbonyl compounds by elimination of the elements of bisulfite with mild base treatment. In situ trapping by 1,3-dienes afforded in good yields a variety of 3,6-dihydro-2H-thiopyrans substituted with electron-withdrawing groups at the 2-position. Exposure of these cycloadducts to strong base at low temperature effected a novel ring contraction, affording 2-(methylthio)-3-cyclopentenes after quenching with methyl iodide. The level of diastereoselectivity exhibited during the generation of these cyclopentenes was found to be dependent on the nature of the electron-withdrawing group at the 2-position of the dihydrothiopyran as well as the substitution pattern originally present in the diene component. In some cases, reducing the temperature during the ring contraction resulted in the isolation of good yields of vinyl cyclopropanes of high isomeric purity. With one substrate, highly diastereoselective rearrangement of a vinyl cyclopropane to a cyclopentene was unambiguously demonstrated, suggesting that this might be a key feature of the overall ring contraction mechanism.Keywords
This publication has 39 references indexed in Scilit:
- Stereochemistry of the Thermal Isomerizations of (1R,2S)-1-(E-1-Propenyl)-2-phenylcyclopropane to 3-Methyl-4-phenylcyclopentenesThe Journal of Organic Chemistry, 1994
- Activated cyclopropanes in the synthesis of five-membered carbocycles and heterocyclesRussian Chemical Reviews, 1993
- Electroorganic chemistry. 138. Electrochemically promoted cyclocoupling of 1,3-dienes or styrenes with aliphatic carboxylic estersThe Journal of Organic Chemistry, 1992
- α-Alkylation of the Diels–Alder cycloadducts of the thioaldehyde, ethyl thioxoacetateJournal of the Chemical Society, Perkin Transactions 1, 1991
- Metalation and alkylation of 3,6-dihydrothiazine 1-oxides prepared via Diels-Alder cycloadditions of N-sulfinyl dienophilesThe Journal of Organic Chemistry, 1991
- The transient dienophile diethyl thioxomalonate and its S-oxide (sulphine) formed by retro-Diels–Alder cleavage reactionsJournal of the Chemical Society, Perkin Transactions 1, 1990
- Anionic approaches to the construction of cyclopentanoidsChemical Reviews, 1989
- 1,4‐Addition of Dihalocarbenes to 1,3‐DienesAngewandte Chemie, 1985
- Reactivity of N-phenacyloxycarbamates and related systems in the presence of bases: study of a new [1,2] anionic rearrangementJournal of the Chemical Society, Perkin Transactions 2, 1983
- Generation of .alpha.-oxo dithioesters by dithiolanium ylide cycloreversion. Synthesis of 2-acyl-3,6-dihydro-2H-thiopyransThe Journal of Organic Chemistry, 1980