Cyclocondensation of amidines with dimethyl acetylenedicarboxylate: A convenient entry into tetramic acids

Amidines undergo cyclocondensations with dimethyl acetylenedicarboxylate (DMAD) to give highly functionalized 5‐dialkylamino‐4‐pyrrolin‐3‐ones. The products are crystalline, highly colored compounds that are uniquely functionalized and represent advanced intermediates in the construction of several other heterocyles, in particular the biologically active tetramic acids. The synthetic transformations of these compounds to tetramic acids are also described.     

Cyclocondensation of 2,2-dichloroethenylbenzamide and its analogs with amidines and hydrogen sulfide in the presence of bases

Available chlorine-containing enamides of the general formula Cl₂C=CHNHCOR (I) easily react with benzamidine and its derivatives to give 1:1 adducts which under heating with sodium methylate transform to 2-(methoxymethyl)-4,5-diaryl-s-triazines. Reaction of compounds (I) with hydrogen sulfide in the presence of triethylamine yields a mixture of products. Only the corresponding 3,5-bis(acylaminomethyl)-1,2,4-tritiolanes were isolated from the reaction mixture in moderate yield.     

Use of a Baylis-Hillman adduct in the stereoselective synthesis of syributins via a RCM protocol

The total synthesis of syributins 1 and 2 using the Baylis-Hillman adduct of 2,3-O-isopropylidene-R-glyceraldehyde-ethyl acrylate as starting material followed by ring closing metathesis (RCM) of the acrylate derivative of the ensuing diol as the key step is reported.     

An expedient aralkylation of Baylis-Hillman adduct via the Pd-catalyzed decarboxylative protonation strategy

An expedient protocol of aralkylation of Baylis-Hillman adducts has been developed. This method used Pd-catalyzed decarboxylative protonation strategy to the allyl ester precursor that was made from the Baylis-Hillman adduct and allyl phenylacetate.     

Reactions with heterocyclic amidines 1. Cyanoethylation of cyclic amidines

2-Amino-5-phenyl-1,3,4-oxadiazole ( 1a ) and 2-amino-1,3,4-thiadiazole ( 1b ) reacted with acrylonitrile to yield β-cyanoethylamino derivatives. On the other hand, 2-amino-4-phenylthiazole ( 2 ) reacted with acrylonitrile under the same experimental conditions to yield a di-β-cyanoethylaminothiazole derivative. 3-Phenyl-Δ²-1,2,4-triazoline-5-thione reacted with acrylonitrile to yield the corresponding adduct. The structure of the adduct was established by its conversion into the acid 13 which could be synthesised via another independent route.     

Cyclocondensation of trifluorolactates with isocyanates

Cyclocondensation of trifluorolactates with isocyanates gives 3-substituted 5-trifluoromethyloxazolidine-2,4-diones.     

Cyclocondensation reaction of a 1,5-diketone with 1,2-diamines

Reaction of 2-acetonyl-4,5-dimethoxy-3′-chlorobenzophenone (1) with ethylenediamine afforded the imidazo[2,1-a]isoquinoline 2, whereas 6-(3-chlorophenyl)-8,9-dimethoxybenzo[b]phenazine (3) and naphthol 4 were obtained with ortho-phenylenediamine.     

Cyclocondensation of 2-methylbenzimidazole with acetylacetone

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1695–1696, December, 1989.     

Enantioselective synthesis of 2-ethyl-2,3-dihydrobenzofuran carboxylic acid, direct precursor of (+)-efaroxan, from a Baylis-Hillman adduct

We describe herein a new and straightforward enantioselective approach to R-(+)-2-ethyl-2,3-dihydrofuran carboxylic acid, the direct precursor of (+)-efaroxan, an α₂ adrenoreceptor antagonist, which is indicated to be used for the treatment of neurodegenerative diseases (Alzheimer and Parkinson), migraine and type II diabetes. Our goal was accomplished using a Baylis-Hillman adduct as starting material. The dihydrobenzofuran acid was obtained in eight steps with an overall yield of 14%.     

Regioselective construction of polysubstituted benzene ring from Baylis-Hillman adduct via [4+2] annulation strategy

A new and regioselective [4+2] benzannulation protocol toward polysubstituted benzenes was developed. Nitroalkane derivative, which was prepared from Baylis-Hillman adduct, served as the four-carbon unit and Michael acceptor as a two-carbon unit.     

Reaction of Β-arylacrylyloxiranes with amidines

Mixtures of stereoisomers of oxiranylhydroxytetrahydropyrimidines were obtained by cyclocondensation of -arylacrylyloxiranes with acetamidines or benzamidines; the 2-aryl derivatives of the products give the corresponding dihydropyrimidines and pyrimidines under base-catalysis conditions. In acetic acid dehydration and oxidation are accompanied by opening of the epoxide ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 652–656, May, 1990.     

Reaction of pyrylium salts with amidines

2,4,6-Substituted pyrimidines were obtained by reaction of 2,4,6-triarylpyrylium perchlorates with amines. 2,4-Substituted pyrimidines were similarly synthesized from 2,6-diphenylpyrylium perchlorate.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 456–458, April, 1978.     

水杨酰腙与磷酰二氯的缩合反应

一些水杨酸的衍生物具有生物活性早有报道.本文研究水杨酰腙与硫代磷酰二氯或磷酰二氯缩合时可能发生的不同关环方式,并通过对反应产物的生物活性测定寻找有效的杀菌剂. 我们发现,在三乙胺存在下水杨酰腙1与硫代磷酰二氯2在四氢呋喃中反应主要以酮式关环生成3类化合物,而与磷酰二氯反应则主要以烯醇式关环生成4类化合物.     

Cyclocondensation of amino-propargyl silanes

Amino-propargyl silanes condense with carbonyl compounds to form imines and subsequently cyclize to form allenylidene tetrahydroquinolines. The cyclocondensations are catalyzed by a variety of Br?nsted acids, among which phosphoric acids provide the highest yields. Subsequent intramolecular and intermolecular additions to the allene moiety provide complex polycyclic amines.     

Reaction of carboxylic acid amidines with ketimines

Diphenyl- and trifluoromethylphenylketimines undergo the Diels-Alder reaction with amidines of benzoic and trichloro- and trifluoroacetic acids to give dihydro-sym-triazines through intermediate azadienes. The structures of the synthesized compounds were proved by means of their IR, PMR, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 842–845, June, 1982.     

Reaction of perfluoroalkyltriazines with amidines of perfluoroalkylcarboxylic acids

Conclusions The amidines of perfluorocarboxylic acids and perfluorotriazines enter into exchange reaction at 20–60° to give an equilibrium mixture with new triazines and amidines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1118–1121, May, 1979.     

Reactions with cyclic amidines II. The behaviour of cyclic amidines toward ethoxycarbonyl and aroyl isothiocyanates

The behaviour of the aminopyrazole derivatives 1a-c, 2-amino-4-phenylthiazole (2) and 2-amino-5-phenyl-1,3,4-thiadiazole (3) toward the action of ethoxycarbonyl and benzoyl iso-thiocyanate is reported. The data clearly demonstrates the dependence of the nature of the products obtained from the reaction of isothiocyanates with cyclic amidines on the nature of the substituents on the heterocyclic ring.