Electrophilic intramolecular cyclization of functional derivatives of unsaturated compounds: IV. Cyclosulfenylation of 5-hexenoic acid amides and nucleophilic cleavage of reaction products

Anilides of 5-hexenoic acid react with arylsulfenyl chlorides in nitromethane in the presence of lithium perchlorate affording products of electrophilic cyclization, N-{6-[(arylsulfanyl)methyl]tetrahydro-2H-pyran-2-ylidene}anilinium perchlorates. The treatment of the latter with sodium acetate or secondary cycloalkylamines in the presence of water results in the opening of the tetrahydropyran ring and provides anilides or cycloalkylamides of 6-arylsulfanyl-5-hydroxyhexanoic acid.     

Electrophilic intramolecular cyclization of functional derivatives of unsaturated compounds: VIII. Cyclization of 4-aryl-<Emphasis Type="Italic">N</Emphasis>-(thiophen-3-yl)but-3-enamides by the action of polyphosphoric acid and chlorosulfanylarenes

Intramolecular cyclization of 4-aryl-N-(thiophen-3-yl)but-3-enamides on heating in polyphosphoric acid afforded 8-aryl-4,6,7,8-tetrahydro-5H-thieno[3,2-b]azepin-5-ones and 5-aryl-1-(thiophen-3-yl)pyrrolidin-2-ones. Cyclofunctionalization of the title compounds with (chlorosulfanyl)benzene and 4-(chlorosulfanyl)-toluene led to the formation of 8-aryl-7-arylsulfanyl-4,6,7,8-tetrahydro-5H-thieno[3,2-b]azepin-5-ones or their mixtures with 5-aryl-4-arylsulfanyltetrahydrofuran-2-ones. 1-(Chlorosulfanyl)-4-nitrobenzene reacted with 4-(4-methylphenyl)-N-(thiophen-3-yl)but-3-enamide and 4-(4-fluorophenyl)-N-(thiophen-3-yl)but-3-enamide to give 5-(4-methylphenyl)-4-(4-nitrophenylsulfanyl)-1-(thiophen-3-yl)pyrrolidin-2-one and 5-(4-fluorophenyl)-4-(4-nitrophenylsulfanyl)tetrahydrofuran-2-one, respectively.     

Synthesis of derivatives of tetrahydrofuran and tetrahydropyran by intramolecular cyclization of unsaturated hydroxy compounds (review)

The literature data on reactions involving electrophilic heterocyclization of , -unsaturated alcohols, 2-allylphenols, oxiranes, aldehydes, and ketones are correlated. The factors that affects the reactivities of the unsaturated compounds (the structure of the substrate, the nature of the electrophile, and the nature of the solvent) in intramolecular cyclization are discussed. The problems of the regioselectivity of the addition and the stereochemistry of the resulting cyclization products are examined, and kinetic data are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1443–1462, November, 1982.     

Radical cyclization cascades of unsaturated Meldrum's acid derivatives

Unsaturated, differentially substituted Meldrum's acid derivatives undergo cascade cyclizations upon ester reduction with SmI(2)-H(2)O. The cascade cyclizations proceed in good yield and with high diastereocontrol and convert simple, achiral starting materials to complex molecular architectures, bearing up to four stereocenters, in a single operation. The cascades are triggered by the generation and trapping of unusual radical-anions formed by electron transfer to the ester carbonyl.     

Microwave-mediated intramolecular Diels-Alder cyclization of biodihydroxylated benzoic acid derivatives

The synthetic utility of biodihydroxylated benzoic acid derivatives for the construction of bridge bicyclo scaffolds was investigated. Biodihydroxylation of benzoic acid using Ralstonia eutropha B9 gave (1S,2R)-1,2-dihydroxycyclohexa-3,5-diene-1-carboxylic acid (DCD) in high optical purity (>95% ee). Protection of the intermediate and subsequent functional group transformation gave the required cyclization precursors in moderate to excellent overall yields. Subsequent intramolecular Diels-Alder cyclization of biodihydroxylated benzoic acid derivatives was carried out using either thermal or microwave conditions. Enantiomerically pure products with five chiral centers were obtained in 4-6 steps from achiral starting material.     

Amidines: synthesis from o-alkenylanilines and cyclization in polyphosphoric acid

Condensation of 2-[(E)-pent-3-en-2-yl]-4-, 2-[(E)-pent-2-en-2-yl]-4-, or 2-(cyclopent-1-enyl)-6-methylaniline with 1-chloro-1-(N-methylimino)- or 1-chloro-1-(N-phenylimino)ethane affords the corresponding amidines. Cyclization of the N-methylimino derivatives in polyphosphoric acid gives 3,4-dihydroquinazolines in high yields.     

Electrophilic intramolecular cyclization of functional derivatives of unsaturated compounds: VI. Reaction of 2-(cyclohex-2-en-1-yl)acetanilides with arylsulfanyl chlorides. Structural and quantum chemical study of isomerization of 2-(2-arylsulfanyl-3-chlorocyclohexyl)acetanilides

2-(Cyclohex-2-en-1-yl)acetanilides react with arylsulfanyl chlorides in chloroform to give 2-(2-arylsulfanyl-3-chlorocyclohexyl)acetanilides which undergo isomerization into 2-chloro-3-arylsulfanylsubstituted derivatives in polar solvents. According to the results of quantum chemical calculations, the addition of arylsulfanyl chlorides to 2-(cyclohex-2-en-1-yl)acetanilides is characterized by negative Gibbs energy. Specific conformation of the isomerization products is stabilized by weak (non-covalent) interactions which make them more energetically favorable than the initial compounds. The reactions of 2-(cyclohex-2-en-1-yl)acetanilides with arylsulfanyl chlorides in nitromethane in the presence of lithium perchlorate lead to the formation of mixtures of the corresponding addition products and electrophilic intramolecular cyclization products, N-[7-(arylsulfanyl)octahydro-1-benzofuran-2-ylidene]anilinium perchlorates, which are converted into free bases by treatment with sodium ethoxide.     

Electrochemical cyclization of unsaturated hydroxy compounds. Part I. Phenylselenoetherification

One-step cyclization of alkenols has been accomplished by electrooxidative phenylselenoetherification. The reaction was performed by electrolysis of unsaturated alcohols and diphenyl diselenide in methylene chloride containing tetraethylammonium bromide.     

Electrochemical cyclization of unsaturated hydroxy compounds. Part II. Phenylselenolactonization

Phenylselenolactonization was performed, in one step, by electrolysis of Δ4- and Δ5 -unsaturated carboxylic acids and diphenyl diselenide in methanol containing ammonium bromide.     

Electrophilic amination of amino acids with N-Boc-oxaziridines: efficient preparation of N-orthogonally diprotected hydrazino acids and piperazic acid derivatives

A general two-step preparation of enantiopure N(alpha),N(beta)-orthogonally diprotected alpha-hydrazino acids 1 is developed on a multigram scale. The key reaction is the efficient electrophilic amination of N-benzyl amino acids 6 with N-Boc-oxaziridine 7 and accommodates various functional groups encountered in side chains of amino acids. The cyclic 2,3,4,5-tetrahydro-3-pyridazine carboxylic acid (piperazic acid) derivatives 2 and 3 or the cyclic 3,4-dihydro-3-pyrazolecarboxylate 4 are conveniently prepared from glutamic acid or aspartic acid via orthogonally diprotected alpha-hydrazino acids 1m and 1n.     

Research on unsaturated azole derivatives III. Electrophilic substitution reactions in the 2-ethynylbenzimidazole series

2-Alkynylbenzimidazoles were obtained by alkylation of 2-benzimidazolylacetylenes with alkyl halides in liquid ammonia in the presence of sodium metal. The strong — I effect of the 2-benzimidazolyl group hindered attack of electrophilic reagents in alkylation and hydration reactions of 2-benzimidazolylacetylenes. Condensation of 2-ethynylbenzimidazoles with bromophenylacetylene under the conditions of the Cadiot-Chodkiewicz reaction gives unsymmetrical diynes.     

Pyridazines. XXXVII. Novel triazanaphthalene derivatives via intramolecular cyclization reactions of vic-disubstituted pyridazines

8-Phenylpyrido[3,4-d]pyridazines bearing various amino substituents at C-5 ( 7a-d, 8 ) were prepared from ethyl 5-benzyl-4-pyridazinecarboxylate 1 via the fused pyridone 5 . The isomeric 4-phenylpyrido[2,3-d]pyridazines having the amino functions attached to C-2 ( 10a-f ) were obtained by a one-pot cyclization of the amino ketone 1 with appropriate acetamide acetals. These novel triazanaphthalene derivatives are of interest as analogues of diuretic and antithrombotic agents.     

Asymmetric synthesis of O-alkylated tetronic acid derivatives via an organocatalytic Mannich reaction and subsequent intramolecular cyclization

The organocatalytic asymmetric Mannich reaction of ethyl 4-chloro-3-oxobutanoate with N-Boc-imines has been studied and Cinchona alkaloids and chiral thiourea-tertiary amines were evaluated as catalysts. A pyrrolidine-based thiourea-tertiary amine was identified as the best catalyst for the transformation. The Mannich adducts readily underwent a one-pot intramolecular cyclization in the presence of triethylamine. A number of O-ethyl tetronic acid derivatives were obtained in good yields and enantioselectivities (up to 91% ee). The products could be further converted to the heteroatomic mimics of prostaglandins via reaction with primary amines.