Synthesis of 2-amino-5,6-dihydro-4H-1,3-thiazines and related compounds by acid catalyzed cyclization of allylic isothiuronium salts

Several allylic isothiuronium salts 6 have been shown to yield 4-substituted 2-amino-5,6-dihydro-4H-1,3-thiazines ( 2 ; R³ = H) and the 2-phenylimino compound 10 on exposure to trifluoroacetic acid or trifluoroacetic acid-stannic chloride. The overall process constitutes a convenient transformation of readily available ketones or aldehydes 3 into the target hetero-cycles. The scope and limitations of this approach are discussed in terms of carbenium ion intermediates ( 7 ). Whereas this method successfully led to the imidazo[2,l-b][1,3]thiazine 13 (93% from 12 ), its application to the synthesis of 2-amino-2-thiazolines (eg. 14 → 15 ) or imidazo-[2,1-b]thiazoles (eg. 16 → 17 ) was unsuccessful. The 2-acetylimino derivatives 9 were found to be useful for purification of the 2-aminothiazines.     

Synthesis of 3-phenoxy-1,3-dihydro-1-isobenzofuranones by palladium-catalyzed carbonylative cyclization of 2-bromobenzaldehyde with phenols

2-Bromobenzaldehyde reacts with phenols in acetonitrile under carbon monoxide pressure in the presence of a catalytic amount of bis(triphenylphosphine)palladium(II) chloride to afford the corresponding 3-phenoxy-1,3-dihydro-1-isobenzofuranones in high yields.     

Synthesis of 4,5-benzotropones by cyclization of 1,3-bis-silyl enol ethers with 1,2-dialdehydes

The cyclization of 1,3-bis-silyl enol ethers or (2,4-dioxobutylidene)triphenylphosphoranes with phthalic dialdehyde allowed a convenient synthesis of a variety of 4,5-benzotropones. The hydrogenation of benzotropones afforded functionalized benzocycloheptanones which were transformed into tricyclic butenolides.     

An Improved Synthesis of 2,2-Dialkyl-1,3-Indanediones

2,2-Dialkyl-1,3-indanediones are useful synthetic intermediates (^1,2) and are know to possess an anticonvulsive activity (³). These compounds are usually prepared by alkylation of 1,3-indanedione under drastic conditions and thus are obtained with low yields (20% to 40%). We describe here a convenient and high yield procedure for the synthesis of symmetrical and unsymmetrical 2,2-dialkyl-1,3-in-danediones based on alkylation of 1,3-indanediones in the presence of celite coated with potassium fluoride (KF-celite). This new reagent has been very recently used to carry out various alkylation reactions (³). We found that KF-celite promotes excellent C-dialkylation (⁴) of 1,3-indanedione la, giving rise to symmetrical 2,2-dialkylated compounds 2a. In the same way, unsymmetrical 2,2-dialkyl-1,3 indanediones 2b can be easily prepared from 2-methyl-1,3-indanedione Ib (⁵).     

Synthesis of 2-substituted 4,5-dihydro-4-oxo-3-furancarboxylates using acylative intramolecular cyclization of sulfonium salts

A simple and efficient synthesis of 4,5-dihydro-4-oxo-3-furancarboxylates using an acylative intramolecular cyclization of sulfonium salts is described. The reaction involved the efficient formation of a mixed anhydride between a linear carboxylic acid and trifluoroacetic anhydride in the presence of N-methylimidazole, followed by the sequential conversion into a highly reactive acylammonium species in situ. This procedure is easily handled, uses readily available inexpensive reagents, and provides a variety of 2-substituted 4,5-dihydro-4-oxo-3-furancarboxylates.     

Facile Synthesis of 1,2-Dialkyl-3-Phenyl-4-Quinolinones

The synthesis of 1,2-dialkyl-3-phenyl-4-quinolinones (1) is readily accomplished by a low-temperature reaction of an N-alkylisatoic anhydride with the therraodynamic potassium enolate of phenyl-acetone. The reaction has also been extended to encompass the synthesis of the more complex 2-(3-hydroxy-propyl)-3-(4-fluorophenyl)-1-methyl-4(1H)-quinolinone (10).     

Synthesis of new 1,3-disubstituted-2,3-dihydro-1H-naphth[1,2e][1,3]oxazines

1,3-Disubstituted-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines were prepared through the ring-closure reactions of the aminobenzylnaphthols with substituted aryl- and heteroarylaldehydes.     

Synthesis of chlorine-containing benzisoindolinium salts by base-catalyzed intramolecular cyclization of ammonium salts

It was shown that dialkylpropargyl/3-(p-chlorophenyl)-2,3-dichloroallyl/ammonium salts in an aqueous alkali medium undergo cyclization-dehydrochlorination to give chlorine-containing benzisoindolinium salts. When the ammonium salt contains simultaneously 3-phenyl (or vinyl)propargyl and 3-(p-chlorophenyl)-2,3-dichloroallyl groups, only the latter enters into the cyclization as the diene fragment.Communication 201 of the series Research on amines and ammonium compounds. See [1] for Communication 197.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1481–1483, November, 1988.     

Synthesis of 1,3,4,5-substituted 1,3-dihydro-2h-imidazol-2-ones

It was shown that 3-(1-methyl-2-oxopropyl)-2-benzoxazolones react with primary amines to form the corresponding 1,3-dihydro-2H-imidazol-2-ones in good yields.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1362–1363, October, 1988.     

Synthesis of 1-heterarylisoquinolines by cyclization of nitrilium salts

1-Heteraryl substituted 3,4-dihydroisoquinolines and their aromatic analogs have been synthesized from heterocyclic carbonitriles, -phenylethyl chloride and tin(IV) chloride.M. V. Lomonosov Moscow State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 376–378, March, 1997.     

Synthesis of 3-substituted-3,4-dihydro-2H-1,3-benzothiazin- 2-ones via a highly regioselective palladium-catalyzed carbonylation of 2-substituted-2,3-dihydro-1,2-benzisothiazoles

A novel synthesis of 3-substituted-3,4-dihydro-2H-1,3-benzothiazin-2-ones is described herein. The strategy relies on a highly regioselective palladium-catalyzed carbonylation of 2-substituted-2,3-dihydro-1,2-benzisothiazoles to give the corresponding 3,4-dihydro-2H-1,3-benzothiazin-2-one derivatives in good to excellent yields.     

Interaction of Alkyl 5,6-Dialkyl-2-amino-3-cyano-4-pyridinecarboxylates with O-Nucleophiles. Synthesis of 6,7-Dialkyl-4-amino-2,3-dihydro-1H-pyrrolo[3,4-c]pyridine-1,3-diones

The reaction of alkyl 5,6-dialkyl-2-amino-3-cyano-4-pyridinecarboxylates with certain O-nucleophiles was investigated, as a result of which 6,7-dialkyl-4-amino-2,3-dihydro-1H-pyrrolo[3,4-c]pyridine-1,3-diones were synthesized.     

Synthesis of 1,3-dihydro-2H-benzimidazol-2-one from 2-aminobenzamide

A method for the synthesis of 2-henzimidazolone ( 1 ) has been devised which does not depend on 1,2-diaminobenzene ( 2 ) as a starting material. This method produces 1 in good yield by the reaction of hypohalite with 2′-carbamoylphthalanilic acid ( 7 ), a compound readily prepared by the reaction of 2-aminobenzamide ( 3 ) and phthalic anhydride. Contrary to prior indications 1 can be hydrolyzed in the presence of acid at temperatures greater than 200 giving excellent yields of 2.     

Synthesis of 1,3-diglycidylimidazolium salts

For the first time, 1,3-diglycidylimidazolium salts were obtained. Their synthesis was accomplished by two routes: the reaction of imidazole with epichlorohydrin in the presence of sodium perchlorate with the subsequent dehydrochlorination of the reaction products with alkalis, and the quaternization of 1-glycidylimidazoles with epichlorohydrin in the presence of salts of strong acids.Institute of Organophysical Chemistry and Carbon Chemistry, National Academy of Sciences of Ukraine, Donetsk 340114. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1062–1066, August, 1996. Original article submitted May 31, 1996.     

Synthesis of 3,5-Diaryl and 3,5-Dialkyl-1,2-dithiolylium-4-olates

Abstract

Sulfurization of 2-acetoxy or 2-benzoyloxy-1,3-propanediones gives the corresponding 1,2-dithiolylium salts which are used as starting materials for preparation of 1,2-dithiolylium-4-olates.

The reaction was studied under different conditions in order to obtain the best sulfurization yields.

A new 3-p-dimethylaminophenyl-5-phenyl-1,2-dithiolylium-4-olate is also described. It is formed by nucleophilic attack on a 3-alkylthio substituted or a 5 unsubstituted position of a 1,2-dithiolylium ion by N, N-dimethylaniline.     

Synthesis of chlorine-substituted naphtho- and benzisoindolinium salts by base-catalyzed intramolecular cyclization of ammonium salts

It was shown that ammonium salts containing a propargyl group together with 3--naphthyl-2,3-dichloroallyl or 3-p-tolyl-2,3-dichloroallyl groups undergo cyclization-dehydrochlorination in an aqueous alkaline medium, forming chlorine-substituted naphthisoindolinium and benzisoindolinium salts. If the 3-phenylpropargyl and 3-p-tolyl-2,3-dichloroallyl groups are both present in the molecule of the ammonium salt the latter group enters exclusively into cyclization as diene fragment.Communication 233 of the series Investigations in the Region of Amines and Ammonium Compounds. For Communication 232, see [1].Institute of Organic Chemistry, National Academy of Sciences of the Armenian Republic, Erevan. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1061–1064, August, 1998.