100281-70-7

Upstream product

• 10181-59-6 2,2,4,4-tetramethyl-3-thioxocyclobutanone 
• 79999-62-5 thiobenzophenone S-methylide 
• 1450-31-3 Thiobenzophenon 
• 23604-61-7 1,1,3,3-tetramethyl-8-thia-5,6-diazaspiro[3.4]oct-5-en-2-one 
• 79999-60-3 2,5-dihydro-2,2-diphenyl-1,3,4-thiadiazole 

Relevant academic research and scientific papers

Aliphatic thiocarbonyl ylides and thiobenzophenone: Experimental study of regiochemistry and methylene transfer in cycloadditions

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 When steric hindrance of 3 increases, the cycloaddition is superseded by 'methylene transfer', i.e., the transfer of the less hindered terminus of 3E-J to the S-atom of thiobenzophenone.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

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.

1,3-CYCLOADDITIONS OF 2,2,4,4-TETRAMETHYLCYCLOBUTANE-1-ONE-3-THIONE S-METHYLIDE

The 1,3,4-thiadiazoline 2, prepared from 2,2,4,4-tetramethylcyclobutane-1-one-3-thione and diazomethane, loses N2 at 40 deg C; the thiocarbonyl ylide 5 is a transient intermediate which in situ undergoes 1,3-dipolar cycloadditions to electron-deficient di

THE ACTIVITY SCALE OF DIPOLAROPHILES VERSUS THIOBENZOPHENONE S-METHYLIDE

Competition experiments of pairs of dipolarophiles for thiobenzophenone (2) furnish relative rate constants which reveal an unusually high selectivity of the nucleophilic 1,3-dipole, in accordance with Sustmann's PMO concept.