A novel rearrangement reaction of 2,5,5-triaryl-2-thiazolin-4-ones during thiation

2,5,5-Triphenyl-2-thiazolin-4-one (7) is transformed by P₂S₅ in boiling dioxane or xylene into N-(3-phenyl-2-benzo[b]thienyl)-thiobenzamide (10). The chloro substituted derivatives 16 and 17 of 7 react analogously but, in the case of 17, a by-product which is believed to be the desired 2-thiazoline-4-thione 18 is also formed. The latter may be isomerised subsequently to 20. The structure of 10 was elucidated mainly by mass spectrometry and X-ray. Various chemical transformations of 10 and its chloro substituted derivatives 19 and 20 are discussed.     

The reaction of N-cyanoamines with 1-(t-butyl)-3,3-diphenylaziridinone: A general method for the synthesis of 1-alkyl-, 1-aralkyl- and 1-aryl-5,5-diphenylhydantoins and -glycocyamidines

N-Cyanomanines react with aziridinone1 to yield the amides2. Base catalysed ring closure of the latter furnished the glycocyamidines3. Acid catalysed de-t-butylation, and deimination combined with de-t-butylation of the compounds3 leads to 1-substituted 5,5-diphenylglycocyamidines (4) and -hydantoins (5), respectively. Part of the hydantoins5 were also directly obtained by hydrochloric acid treatment of amides2. Selective de-t-butylation in position 3 of the glycocyamidine3 (R = t-Bu) was brought about by heating with methanolic NH₃ in the presence of NH₄I. Reaction of1 with the un substituted N-cyanoamine furnished carbodiimide7 which was cyclized to the glycocyamidine8. The mass spectra of some glycocyamidines4 and hydantoins5, as well as of compounds7 and8 are discussed.     

Electron deficient heteroaromatic ammonioamidates—XVI: The synthesis and photochemistry of ethyl N-(2-methyl-4-methylene-6,7-methylenedioxy- 3,4-dihydro-3-quinazolinyl)-N-phenylcarbamate

Irradiation through Pyrex of the N-(dihydroquinazolinyl)carbamate 3c in ethanol furnishes mixtures (Scheme 1) of two photoisomers (2c and 4a), two dimeric products: the 1,2-bis(4-quinazolinyl)ethane 5 and the (p-phenylene)dicarbamate 6, and of ethyl N-phenylcarbamate. The latter, as well as compounds 4a and 5 are formed also on irradiation of compound 2c. The radicals 9 and 10, formed by homolysis of the N-N bond of 3c as well as of the CH₂-N bond of 2c are considered to be the primary photoproducts of both reactions, and to lead, by various recombination processes, to compounds 2c, 4a, 5 and 6, and to ethyl N-phenylcarbamate by hydrogen abstraction. It is not clear at present whether concerted photochemical [1,3] shifts contribute to the formation of 2c and 4a.     

The annular desmotropy of S-methyl-5,5-diphenyl-2-thiohydantoin

The separate existence of two individual desmotropic forms (2a and b) of the S-Me derivative of 5,5-diphenylthiohydantoin which had been originally claimed on the basis of IR evidence, has been proved by X-ray molecular structure determination. This is the established case of annular desmotropy in the azole field.     

Robust reasoning with agent-based modeling

Agent-based modeling (ABM) is a powerful representational formalism that has wide utility for modeling nonlinear systems. For ABM to achieve its potential as a scientific tool, our ability to build models that embody our knowledge must be complemented by rigorous means for making inferences using such models. Due to nonlinearity, this rigor cannot in general be based solely on demonstrating that a model reliably predicts the outcomes of available physical measurements. In this paper we describe an alternative approach to robust reasoning based on the concept of ensembles of alternative models. Ensembles of models can be defined that plausibly span classes of systems including the system of interest. Research methodologies for searching and sampling from such ensembles can be used to support plausible conclusions about invariant properties of ensembles of ABMs and hence of the classes of systems they represent. Notable among these are approaches that implement a competition between ensembles of problem formulations or challenges and conclusions robust to these challenges. This approach is demonstrated using examples drawn from our research.     

Hydantoins,thiohydantoins, glycocyamidines—36: 1,5,5- and 3,5,5-triphenyl derivatives

In contrast to the α-chloroamides 1a-c which, when reacted with potassium N-cyanoanilide, furnish anomalous substitution products (2a-c), the related nitrile and ester yields normal substitution products (3a and b) under the same conditions. 1,5,5-Triphenylhydantoin (4a) and a series (5a-8a, 13 and 14) of its derivatives have been prepared starting with 3a and b. Acid hydrolysis of 3a yields, in addition to the normal products (4a and 5a) considerable quantities of the rearranged product 4b. An authentic sample of the latter, as well as a series of its derivatives (5b-8b and 11) have been prepared starting with α,α-diphenylglycinonitrile and 2-methylthio-1,4,4-triphenyl-2-imidazolin-5-one (9). When reacted with ammonia and ammonium iodide, 9 gave, in addition to the normal ammonolysis product 7b, the Dimroth rearrangement product 16, as well as 5,5-diphenylglycocyamidine, by apparent dephenylation of 16. The mass spectra of the imidazole derivatives 4–8, a and b, 9, 11, 13 and 14 are discussed.     

Benzoxadiazocines,benzothiadiazocines and benzotriazocines-IV : Ring closure of 1-(2-[n-(2-chloroethyl and 2-hydroxyethyl)-n-methylamino]phenyl)-3-phenylthioureas. tetrahydroquinoxaline vs.dihydro-3,1,6-benzothiadiazocine and hexahydro-1,3,6-benzotriazocinethione formation

While base induced ring closure of 1-(2-[N-(alkylsulfonyl and arylsulfonyl)-N-(2-chloroethyl)amino]phenyl)-3-phenylthioureas 1 had furnished the corresponding type 2 dihydro-3,1,6-benzothiadiazocine derivatives rather than the isomeric hexahydro-1,3,6-benzotriazocinethiones (3) or tetrahydroquinoxalines (4), base induced ring closure of the related N-(2-chloroethyl)-N-Me derivatives 9a-9c, 10a and lOb furnishes type 14 tetrahydroquinoxalines. 14a is obtained also by treating the N-(2-hydroxyethyl)-N-Me derivative 11 with the triphenylphosphine-diethyl azodicarboxylate (DEAD) reagent. In situ replacement of the chlorine atom of compound 9a by iodine in the absence of base as well as treatment of 1-(2-[N-(2-hydroxyethyl)-N-methylamino]phenyl)-1-methyl-3-phenylthiourea (18) with the triphenyl-phosphine-DEAD reagent furnishes the benzimidazole derivatives 16 and 22, respectively, whose formation may be rationalised by assuming the intermediacy of the dihydro- and tetrahydro-3,1,6-benzothiadiazocine derivatives 12a · HI and 20, respectively, and their subsequent ring contraction.     

The reaction of α-chloro-α,α-diphenylacetamides with potassium n-cyanoanilide: A novel type of cine substitution

Three types of products are formed in the reactions of α-chloro-α,α-diphenylacetamides (1a–c with potassium N-cyanoanilide: cine substitution products of type 2 as the main products, and two types of normal products (4a and b, and 3, 6 and 7a, respectively) whose formation reflects the ambident reactivity of the N-cyanoanilide anion.     

Condensed 1,3,5-triazepines—II : The synthesis of 2,3-dihydro-1H-imidazo[1,2-a] [1,3,5]benzotriazepin-5(6H)-ones and -thiones

A method, based on the reaction of 1-(2-aminoaryl)-2-iminoimidazolidines 8 with phosgen, 1,1′-carbonydiimidazole and thiophosgene, carbon disulfide and 1,1′-thiocarbonyldiimidazole, respectively, has been devised for the synthesis of the title compounds. The compounds 8 are rearranged at elevated temperatures into the isomeric 2-amino-1-(2-amino-ethyl) benzimidazoles 11.