88691-94-5

Upstream product

• 186581-53-3 diazomethane 
• 60-29-7 diethyl ether 
• 15719-64-9 methylammonium carbonate 
• 1450-31-3 Thiobenzophenon 
• 64035-64-9 Trimethylsilylmethyl trifluoromethanesulfonate 
• 79999-60-3 2,5-dihydro-2,2-diphenyl-1,3,4-thiadiazole 
• 79999-62-5 thiobenzophenone S-methylide 
• 127411-34-1 2,2-Di-tert-butyl-2,5-dihydro-[1,3,4]thiadiazole 
• 104659-50-9 2',5'-dihydrospiro[fenchane-2,2'-(1,3,4)-thiadiazole] 
• 125593-36-4 2,2',3,5'-tetrahydro-1,1,3,3-tetramethylspiro[1H-indene-2,2'-[1,3,4]thiadiazole] 
• 473617-37-7 6,6,9,9-tetramethyl-4-thia-1,2-diazaspiro[4,4]non-1-ene 
• 23604-61-7 1,1,3,3-tetramethyl-8-thia-5,6-diazaspiro[3.4]oct-5-en-2-one 
• 23695-65-0 adamantane-2-thione 

Downstream Products

• 632-51-9 1,1,2,2-tetraphenylethylene 
• 530-48-3 1,1-Diphenylethylene 
• 1450-31-3 Thiobenzophenon 

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 When steric hindrance of 3 increases, the cycloaddition is superseded by 'methylene transfer', i.e., the transfer of the less hindered terminus of 3E-J to the S-atom of thiobenzophenone.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

Thiofenchone S-methylide and its spiro-1,3,4-thiadiazoline precursor

Spiro[fenchane-2,2′-(1,3,4)-thiadiazoline] (6), prepared from thiofenchone and diazomethane, extrudes N2(t1/2 22 min, 46°C, toluene) and furnishes the S-methylide 7 which, in turn, closes the thiirane ring or else is intercepted by 1,3-cycloadditions to dipolarophiles (tetracyanoethylene, maleic anhydride, N-methyl-1,2,4-triazoline-3,5-dione, aromatic thioketones). When thiocarbonyl S-methylide 7 is set free in methanol, fenchone S,O-dimethylacetal is formed as an HX adduct. Catalysis by acetic acid converts 7 to 1-(methylthio)-α-fenchene (25) by way of a Wagner-Meerwein rearrangement. The addition of diazomethane to thiocampher leads, via thiadiazoline 12, to thiocamphor S-methylide; the latter undergoes a 1,4-H shift, thus affording 2-methylthio-2-bornene (11).

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-Dipolar cycloadditions, 116. The formation of 1,3-dithiolanes from aromatic thioketones and diazomethane - The mechanism of the Schonberg Reaction

Reactions of diaryl thioketones with diazomethane at room temperature afford 4,4,5,5-tetraaryl-1,3-dithiolanes; the scope of this surprising 2:1 interaction has been studied for decades (Schonberg Reaction). The clue to the mechanism was our observation that the stoichiometry is 1:1 at -78 °C, and 2,5-dihydro-2,2-diaryl-1,3,4-thiadiazoles are formed as primary [2+3] cycloadducts. They lose N2 at -45 °C in first-order reactions generating diaryl thioketone S-methylides which can be intercepted by thioketones (→1,3-dithiolanes), multiple CC bonds, or acids HX. In the absence of trapping reagents, the elusive intermediates either dimerize furnishing 2,2,3,3-tetraaryl-1,4-dithianes or give rise to 2,2-diaryl-thiiranes by electrocyclization. Beyond thiobenzophenone and diazomethane, our main model reaction, the studies involve fluorene-9-thione, 4,4-dimethoxy- and 4,4- dichloro-thiobenzophenone. The ring of 2,5-dihydro-2,2-diphenyl-1,3,4- thiadiazole (8) is opened by LDA at -78 °C and derivatives of anion 12 are obtained. - In summa: The Schonberg reaction consists of two 1,3-dipolar cycloadditions, linked by a 1,3-dipolar cycloreversion.

Cycloadditions of dialkyl thioketone-S-methylides

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

A Simple Method for Generation of Thiocarbonyl Ylides and Their Regioselective 1,3-Cycloadditions

Thioketone S-methylides were generated from thioketones and (trimethylsilyl)methyl triflate, and underwent 1,3-cycloaddition with thioketones to give 1,3-dithiolanes.

THE CHEMISTRY OF 1,3,4-THIADIAZOLINE-2-SPIRO-2'-FENCHANE.

Diazomethane adds to one of the two faces of the sterically hindered thiofenchone furnishing the title compound wich extrudes N2 at 46 deg C whith t1/2=22 min; the thiofenchone S-methylide is intercepted by dipolarophiles and acts as a base in reactions with methanol, thiophenol and acetic acid, in the latter case accompanied by skeletal rearrangement.

NEW THIOCARBONYL YLIDES FROM THIOBENZOPHENONE

Thiobenzophenone is converted to 1,3,4-thiadiazolines by reaction with diazoethane, phenyldiazomethane or diphenyldiazomethane at -78 deg C.Extrusion of nitrogen from the thiadiazolines furnishes thiocarbonyl ylides which, in turn, undergo electrocyclic r

NEW REACTIONS OF THIOBENZOPHENONE S-METHYLIDE

2,2-Diphenyl-1,3,4-thiadiazoline, prepared from thiobenzophenone and diazomethane at -78 deg C, extrudes N2 at -45 deg C and allows to study in situ 1,3-cycloadditions of thiobenzophenone S-methylide (3) with electrophilic C=S, C=C, CC, and N=N bonds.

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.