- Continuous Flow Synthesis of 2H-Thiopyrans via thia-Diels–Alder Reactions of Photochemically Generated Thioaldehydes
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Herein, we report a novel protocol for the photochemical generation of thioaldehydes in a continuous flow process which were in situ reacted with electron rich 1,3-butadienes in thia-Diels–Alder reactions. A broad range of 3,6-dihydro-2H-thiopyrans were formed as products in much higher yields and productivities as compared to classical batch processes. Moreover, greatly reduced reaction times and a facile large-scale preparation of products were achieved by fully exploiting the advantages of continuous flow technology.
- Sachse, Florian,Gebauer, Konrad,Schneider, Christoph
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supporting information
p. 64 - 71
(2020/11/30)
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- Protiodesilylation of 3-trimethylsilyl-2-thiabicyclo[2.2.1]hept-5-enes and derivatives: A stereochemical study
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endo- and exo-trimethylsilyl-3-phenyl-2-thiabicyclo[2.2.1]hept-5-enes, the endo-trimethylsilyl-exo-S-oxide and their S,S-dioxide derivatives were protiodesilylated with fluoride ion. Stereoconvergent reactions were found, affording the endo-phenyl derivatives. These results can be rationalised with the hypothesis of a common carbanionic intermediate. In contrast, the desilylation of 3-endo-trimethylsilyl-3-exo-phenyl-2-thiabicyclo[2.2.1]heptane gave a mixture of endo- and exo-isomers, thus proving the involvement of the double bond in the control of the reaction stereoselectivity.
- Bonini, Bianca F.,Masi, Enza,Masiero, Stefano,Mazzanti, Germana,Zani, Paolo
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p. 3553 - 3562
(2007/10/03)
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- STEREOCHEMISTRY OF PROTIODESILYLATION OF 3-TRIMETHYLSILYL-2-THIABICYCLOHEPTENES, HEPTANES AND DERIVATIVES.
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Some 3-trimethylsilyl-2-thiabicycloheptenes and heptanes of known configuration were protiodesilylated and the stereochemistry of the reaction was studied.Evidences for a carbanionic intermediate as well as the pivotal role played by the metal coun
- Bonini, Bianca Flavia,Masi, Enza,Masiero, Stefano,Mazzanti, Germana,Zani, Paolo
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p. 379 - 380
(2007/10/02)
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- Formation of Thiocarbonyl Compounds in the Reaction of Ebselen Oxide with Thiols
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Reaction of α-toluenethiol with Ebselen oxide, 2, affords dibenzyl disulfide and seleno sulfide 5, R = PhCH2.In the course of this reaction, thiobenzaldehyde is formed and can be trapped with cyclopentadiene in 90percent yield.Reaction of 2-propene-1-thiol with 2 afforded thioacrolein dimer in 69percent yield and seleno sulfide 5, R = CH2-CH=CH2.Trapping, stereochemical, and isotopic exchange studies were used to determine if in the reaction of 2 with 1-heptanethiol, cyclohexanethiol, and N-acetyl-D,L-cysteine thiocarbonyl compounds heptanethial, cyclohexanethione, and 2-acetamino-3-thioxopropanoic acid (α-thioformyl-N-acetylglycine), respectively, are also formed.These studies showed that free thiocarbonyl compounds are not formed in these reactions.
- Glass, Richard S.,Farooqui, Firdous,Sabahi, Mahmood,Ehler, Kenneth W.
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p. 1092 - 1097
(2007/10/02)
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- Diastereoselectivity in the Diels-Alder Reactions of Thioaldehydes
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The Diels-Alder reaction of thioaldehydes with cyclopentadiene occurs with a preference for the endo isomer.The highest selectivity is observed for thioaldehydes RCHS where R is a bulky group such as tert-butyl or isopropyl.Thioaldehydes having α-alkoxy, acetoxy, or siloxy substituents also react with useful endo selectivity.Secondary orbital overlap is a small factor in these reactions since α-oxo thioaldehydes react with relatively low endo selectivity.Steric effects are primarily responsible for the endo preferences observed.The Diels-Alder reactions of chiral α-oxygen substituted thioaldehydes also occur with useful thioformyl face selectivity.A Cornforth transition state 5 is most likely for the selectivity observed for α-alkoxy or acetoxy thioaldehydes, but the α-hydroxy analogue 23 reacts with the opposite facial preference.The highest face selectivity is obtained with the acetonide of thioglyceraldehyde, generated by photolysis of the phenacyl sulfide 15b.
- Vedejs, E.,Stults, J. S.,Wilde, R. G.
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p. 5452 - 5460
(2007/10/02)
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- Thioaldehyde Diels-Alder Reactions
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Thioaldehydes containing virtually any α-substitutent can be generated by photofragmentation of phenacyl sulfides.Donor-substituted derivatives are reactive toward electron-rich dienes and give 2 + 4 cycloadducts with regiochemistry corresponding to advan
- Vedejs, E.,Eberlein, T. H.,Mazur, D. J.,McClure, C. K.,Perry, D. A.,et al.
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p. 1556 - 1562
(2007/10/02)
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- GENERATION OF THIOALDEHYDES VIA FLUORIDE INDUCED ELIMINATION OF Α-SILYLDISULFIDES
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A mild, efficient and general method for the generation of reactive thioaldehydes from α-silyldisulfides is described.
- Krafft, Grant A.,Meinke, Peter T.
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p. 1947 - 1950
(2007/10/02)
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- Transformation of Thiosulphonates into α-Sulphonyldisulphides, a New Class of Thioaldehyde Precursors
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Toluene-p-thiosulphonates, RCH2SSO2Tol (1) where R is an electron-withdrawing group, are transformed readily into α-sulphonyldisulphides (2) which, with triethylamine, undergo fragmentation-elimination to give 2 moles of thioaldehydes, RCHS.
- Kirby, Gordon W.,Lochead, Alistair W.,Sheldrake, Gary N.
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p. 1469 - 1470
(2007/10/02)
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