88793-71-9

Upstream product

• 1117-96-0 Diazoethan 
• 1450-31-3 Thiobenzophenon 
• 251902-82-6 2',5'-dihydro-2,2,4,4,5'-pentamethylspiro[cyclobutane-3,2'-(1,3,4)-thiadiazole]-1-one 
• 855701-98-3 2,5-dihydro-1,3,4-thiadiazole 
• 855702-00-0 C₁₅H₂₀N₂S 

Relevant academic research and scientific papers

Diradical reaction mechanisms in [3 + 2]-cycloadditions of hetaryl thioketones with alkyl- or trimethylsilyl-substituted diazomethanes

Reactions of dihetaryl and aryl/hetaryl thioketones with 2-diazopropane, diazoethane, and (trimethylsilyl)diazomethane were studied at variable temperature. The experiments showed that reactions with 2-diazopropane carried out at -75°C occur mainly via th

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 When steric hindrance of 3 increases, the cycloaddition is superseded by 'methylene transfer', i.e., the transfer of the less hindered terminus of 3E-J to the S-atom of thiobenzophenone.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

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