88691-94-5Relevant articles and documents
Aliphatic thiocarbonyl ylides and thiobenzophenone: Experimental study of regiochemistry and methylene transfer in cycloadditions
Huisgen, Rolf,Mloston, Grzegorz,Giera, Henry,Langhals, Elke,Polborn, Kurt,Sustmann, Reiner
, p. 1519 - 1531 (2007/10/03)
1,3-Dipolar cycloadditions of aliphatic or alicyclic thiocarbonyl ylides 3A-D - sterically hindered at least at one terminus - with thiobenzophenone produce both regioisomeric 1,3-dithiolanes 4 and 5. According to quantum-chemical calculations (preceding paper), a concerted cycloaddition furnishing 2,4-substituted dithiolanes 4 competes with the formation of an intermediate C,C-biradical 9 which cyclizes to the more crowded 4,5-substituted dithiolanes 5. When steric hindrance of 3 increases, the cycloaddition is superseded by 'methylene transfer', i.e., the transfer of the less hindered terminus of 3E-J to the S-atom of thiobenzophenone. The thiobenzophenone S-alkylide 11, thus formed, rapidly reacts with a second molecule ofthiobenzophenone to generate the 4,4,5,5-tetraphenyl-1,3-dithiolane 12 via the highly stabilized C,C-biradical 10. Methylene transfer occurs when the cyclization of the mixed C,C-biradical 9 requires a higher activation barrier than its dissociation to aliphatic thioketone + 11; the threshold is surprisingly well reproduced by calculations. The structural assignment of sixteen 1,3-dithiolanes is based on their formation from corresponding reactant pairs as well as on 1H and 13C chemical shifts. X-ray diffraction analyses of three spiro-1,3-dithiolanes reveal the van der Waals strain in non-bonded interactions, folding angles, shearing forces, and bond lengths. Comparison of the mass spectra of many 1,3-dithiolanes allows the reconstruction of major fragmentation pathways. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
1,3-Dipolar cycloadditions, 117. Reactions of thiobenzophenone S- methylide with thiocarbonyl compounds
Huisgen, Rolf,Li, Xingya,Mloston, Grzegorz,Fulka, Claudia
, p. 1695 - 1702 (2007/10/03)
2,5-Dihydro-2,2-diphenyl-1,3,4-thiadiazole (4) eliminates N2 at -45 °C and generates thiobenzophenone S-methylide (5), which is intercepted by dipolarophiles. The 1,3-cycloadditions of 5 with thiones (aromatic and aliphatic thioketones, dithioesters, trithiocarbonate) furnish 1,3- dithiolanes 7, in which the substituents, even voluminous ones, appear in the proximal 4- and 5-positions. The reaction of 5 with adamant-anethione furnishes 7h and 4,4,5,5-tetraphenyl-1,3-dithiolane (7a) in a ratio of 4:1; a methylene transfer is involved, and the mechanistic pathways are discussed. The cycloadduct 7f originating from 5 and diphenyl trithiocarbonate undergoes an isomerization which consists of ionization and ring-opening leading to a ketene dithioacetal structure.
Cycloadditions of dialkyl thioketone-S-methylides
Huisgen,Mloston
, p. 7041 - 7044 (2007/10/02)
Various mechanistic criteria were employed in the effort to establish the borderline between one-step and two-step pathways in the reactions of two thiocarbonyl ylides, diisopropyl, and di-ter-butyl thioketone-S-methylide, with electron-deficient alkenes
