- Photoelectron spectra and molecular properties CXXII. The low first ionization energies of the β-trimethylsilyl substituted sulfides (H3C)3SiH2CSCH2Si(CH3)3 and ((H3C)3Si)3CSCH3 and their rationalization
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The rather low first vertical ionization energies of bis(trimethylsilylmethyl)sulfide, IE1 V = 8.04 eV, and tris(trimethylsilyl)methylmethyl sulfide, IE1 V = 7.66 eV, are compared with those of other alkyl, silylalkyl and silylsulfides and shown further to confirm the small influence of α-trimethylsilyl groups and of the very large donor effect of β-trimethylsilyl substituents in the ground state of radical cations.The overall 2.8 eV (!) lowering of the sulfur ? lone pair ionization and of the individual, mostly non-additive, substituent effects, are rationalized in terms of a qualitative approach based on the electron distribution in the ground state of the neutral molecules.
- Bock, Hans,Meuret, Jochen,Stein, Udo
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- Synthetic Entry to Polyfunctionalized Molecules through the [3+2]-Cycloaddition of Thiocarbonyl Ylides
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Here we present a comprehensive study on the [3+2]-cycloaddition of thiocarbonyl ylides with a wide variety of alkenes and alkynes. The obtained dihydro- and tetrahydrothiophene products serve as exceptionally versatile intermediates providing access to thiophenes, dienes, dendralenes, and vic-quarternary carbon centers. The use of high-pressure conditions enables thermally unstable, sterically encumbered or moderately reactive substrates to undergo the cycloaddition under mild conditions, thereby increasing the yield by up to 58percent. In addition, we showcase its utility by the formal syntheses of the pharmaceuticals NGB 4420 and tenilapine.
- Habiger, Christoph,Haut, Franz-Lucas,Korber, Johannes Nepomuk,Müller, Thomas,Magauer, Thomas,Mayer, Peter,Speck, Klaus,Wurst, Klaus
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supporting information
(2019/09/06)
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- COMMERCIALLY VIABLE SYNTHESIS OF CANTHARIDIN AND BIOACTIVE CANTHARIDIN DERIVATIVES
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The present disclosure provides methods for synthesizing cantharidin and cantharidin derivatives.
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Paragraph 0105
(2016/07/05)
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- Synthetic Applications of 3,4-Bis(trimethylsilyl)thiophene: Unsymmetrically 3,4-Disubstituted Thiophenes and 3.4-Didehydrothiophene
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3,4-Bis(trimethylsilyl)thiophene (1a) was synthesized by three routes: (a) 1,3-dipolar cycloaddition; (b) modification of 3,4-dibromothiophene; and (c) intermolecular thiazole-alkyne Diels-Alder reaction. 3,4-Bis(trimethylsilyl)thiophene (1a) can function as a versatile building block for the construction of unsymmetrically 3,4-disubstituted thiophenes utilizing its step wise regiospecific mono-ipso-substitution followed by palladium-catalyzed cross-coupling reactions. In this manner, thiophenes 15, 16, 17a-j, 19a,b, 20, 22a-c, 23a,b, 24a-d, 25a-c, and 27a-j were prepared. The thiophene-3,4-diyl dimer 28 and thiophene-3,4-diyl tetramer 29 were also realized by palladium-catalyzed self-coupling reaction of organoboroxines. The stannylthiophene 31, formed by conversion of the C-Si bond to a C-Sn bond via boroxine 26c underwent both carbonylative coupling and lithiation followed by quenching with electrophiles to afford unsymmetrically 3,4-disubstituted thiophenes 33 and 36a-c as well. Moreover, 3,4-bis(trimethylsilyl)thiophene (1a) can be used as the starting material for the generation of the highly strained cyclic cumulene 3,4-didehy-drothiophene (2), whose existence was substantiated by its trapping reaction with several alkenes.
- Ye, Xin-Shan,Wong, Henry N. C.
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p. 1940 - 1954
(2007/10/03)
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- Thiocarbonyl Ylides. VI. New Generation of Thiocarbonyl Ylides from Organosilicon Compounds Containing Sulfur and Their 1,3-Cycloadditions
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Thermolysis of bromo(trimethylsilyl)methyltrimethylsilylmethyl sulfide was found to give a thiocarbonyl ylide, the 1,3-cycloaddition of which proved a new method for the synthesis of tetrahydrothiophenes.The effect of the silyl group of the ylide on the regio- and stereoselectivity in these 1,3-dipolar cycloaddtions is discussed.Keywords---thiocarbonyl ylide; 1,3-cycloaddition; organosilicon compound; thermolysis; tetrahydrothiophene; regioselectivity
- Terao, Yoshiyasu,Aono, Masahiro,Imai, Nobuyuki,Achiwa, Kazuo
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p. 1734 - 1740
(2007/10/02)
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