The Preparation of Parabanic Acids from 1,1,3-Trisubstituted Ureas via a Hofmann Elimination Reaction

Abstract

during Stobbe condensations.4 However, the migration of the double bond of VId or Vlld (yielding VIII after saponification) should be more favored than the case of Via or Vila since the proton which must be abstracted is further removed from the carboxylate anion.

Synthesis, X-ray crystal structure and spectroscopic characterization of the new dithiolene [Pd(Et2timdt)2] and of its adduct with molecular diiodine [Pd(Et2timdt)2]·I2·CHCl3 (Et2timdt = monoanion of 1,3-diethylimidazolidine-2,4,5-trithione)

“…It has already been shown that cyclic pentaatomic vicinal dithiones are not isolable, 23,24 therefore any conventional method of synthesis starting from them is not suitable for the preparation of [M(R 1 2 timdt) 2 ] dithiolenes. To overcome this obstacle, we have developed a one-step route leading to the complex 4 based on the sulfuration of 1,3-dialkylimidazolidine-2-thione-4,5-diones 25 (1) with Lawesson's reagent 26 (2) in the presence of a metal halide or metal powder (Scheme 1). 8,9 However, the yields of these reactions are generally low owing to the formation of several by-products, among which the tetrathiocino derivatives 27 (3) and the trans-bis[O-alkyl (4-methoxyphenyl)phosphonodithioate 28 (5) have been identified.…”

“…Method (a). A mixture of 1,3-diethylimidazolidine-2-thione-4,5-dione 18 (1, R = Et; 1 g, 5.38 mmol), an equivalent amount of Lawesson's reagent (2) and a little excess of Pd powder was refluxed in anhydrous toluene (100 mL) for 8 h. The concentrated suspension was poured in about 100 mL of MeOH, from which, after 3 h at 4 ЊC, the solid was filtered, dried and extracted for 2 days with CHCl 3 in a Soxhlet apparatus (0.274 g, 18% yield).…”

New [M(R,R‘timdt)2] Metal-Dithiolenes and Related Compounds (M = Ni, Pd, Pt; R,R‘timdt = Monoanion of Disubstituted Imidazolidine-2,4,5-trithiones): An Experimental and Theoretical Investigation

“…Disubstituted Imidazolidine-2-thione-4,5-thiones (4a − j). These products were prepared according to literature methods by reacting an appropriate N,N ‘-dialkylthiourea or N -alkyl- N ‘ -arylthiourea with oxalyl chloride in CH 2 Cl 2 solution and were recrystallized from CH 2 Cl 2 or ethyl ether.…”

Efficient One-Pot Synthesis of Unsymmetrical 2-Thioparabanic Acids from Oxalyl Chloride, Benzoyl Isothiocyanate, and Primary Amines

“…The reaction occurs by attack of oxalyl chloride on the sulfur atom of the thiourea to form the isomeric iminothiazolidine-4,5-dione, which gradually forms on standing, or more rapidly on heating, a yellow solid identified as the 2-thioparabanic acid. 11 As part of our current studies on the development of new routes in heterocyclic synthesis, [12][13][14][15] we report herein an efficient one-pot synthesis of unsymmetrical 2-thioparabanic acids 16 from primary amines, benzoyl isothiocyanate, and oxalyl chloride (Scheme 1).…”