Synthesis of 2-methylidene-1-silacyclohexanes by intramolecular hydrosilylation

The preparation of various (hex-5-ynyl)silanes was achieved following two different synthetic approaches from readily available materials such as 4-bromobutene, 6-iodohexyne and chlorosilanes. Different reaction conditions for intramolecular hydrosilylation were tested to prepare the corresponding 2-methylidene-1-silacyclohexanes. Notably, the use of Speier’s catalyst allowed the regioselective formation of the desired products in moderate yields.     

Synthesis and Stereochemistry of Substituted 1,3-Dioxa-2-silacyclohexanes: VII. Synthesis and Stereochemistry of Substituted 2-Vinyl-2-methyl-1,3-dioxa-2-silacyclohexanes

The stereochemistry of substituted 2-vinyl-2-methyl-1,3-dioxa-2-silacyclohexanes was studied by ^1Hand ^13C NMR spectroscopy. The configurational and conformational assignment of a mixture of 2-vinyl-2,4-dimethyl-1,3-dioxa-2-silacyclohexane diastereomers with various ratios of the cis and trans forms was made. The molecules of both conformers occur chiefly in the chair conformartion with equatorial location of the methyl group at the C⁴ atom. The experimental data were confirmed by AM1 and MM+ optimization of the molecular geometry.     

Synthesis of 5-methylidene-2-thio- and 2-selenohydantoins from isothiocyanates or isoselenocyanates and l-serine

3-Aryl-5-methylidenethiohydantoins and 3-aryl-5-methylidene-selenohydantoins were obtained by one-pot reaction of aryl isothiocyanates or isoselenocyanates with l-serine in NaOH–H₂O–Py mixture followed by room temperature HCl-promoted dehydration.     

Ozonides of perfluorooct-1-ene and perfluorooct-2-ene

Ozonides of higher perfluoroalkenes were prepared for the first time by ozonation of perfluorooct-1-and-2-enes in Freon-113. The structures of the resulting compounds were confirmed by¹³C NMR spectroscopy and GLC-mass spectrometry.     

Palladium-catalyzed synthesis of carbazoles from N-(2-halophenyl)-2,6-diisopropylanilines via C-C cleavage

The synthesis of 1-isopropyl-substituted carbazoles by the palladium-catalyzed dealkylative cyclization of N-(2-halophenyl)-2,6-diisopropylanilines is described. The reaction involves intramolecular C-C bond formation, coupled with the cleavage of a C-X bond and a C-C bond, and is proposed to proceed through the formation of a dearomatized intermediate.     

One-pot preparation of 2-(alkyl)arylbenzoselenazoles from the corresponding N-(acetyl)benzoyl-2-iodoanilines via a microwave-assisted methodology

We report here the first example of a one-pot synthesis of 2-(alkyl)arylbenzoselenazoles from N-(acetyl)benzoyl-2-iodoanilines. The reaction was carried out in the presence of Woollins’ reagent under microwave irradiation and resulted in moderate to good yields.     

Novel Synthesis of Condensed Pyridin-2(1H)-one and Pyrimidine Derivatives

The reaction of N-chloroacetyl derivatives 6-10 with morpholine yielded N-morpholin-1-yl acetyl derivatives 11-15 , which were subjected to Thorpe-Zieler cyclization with sodium tert -butoxide to produce the corresponding condensed pyridin-2(1H)-one derivatives 16-20 . Treatment of compounds 1 , 6-10 with either malononitrile or p -chlorobenzylidinemalononitrile in presence of triethylamine, afforded the corresponding pyrimidines 21-25 , 27 and pyridine derivative 26 respectively. Moreover compound 1 a was treated with ethyl isothiocyanoacetate to give the corresponding piprazine derivative 28 .     

Lead-promoted Barbier-type reaction of aldehydes with propargyl bromides in aqueous media

This paper reports that the reaction of the propargyl bromides with aldehydes promoted by powdered lead in aqueous media.The selectivity and possible mechanism of these reactions are discussed.The yields of products for reaction of propargyl bromide are 31~71%.The ratios of al-lenyl alcohol and homopropargyl alcohol are 1:1.5 to 1:3.The product for reaction of phenyl propargyl bromide is allenyl alcohol and the yields are 52~84%.     

2-异丙基-1,3-二氢-4(1H)异喹啉酮及其衍生物的合成

报道了异喹啉酮与格氏试剂反应合成四氢-4-羟基异喹啉酮化合物,NBS和混酸(HNO~3/HAc)与异喹啉酮反应合成异喹啉酮衍生物。6个新化合物的结构,通过元素分析,红外光谱和核磁共振氢谱,质谱给予证实。     

Synthesis, NMR characterization and reactivity of 1-silacyclohex-2-ene derivatives

The chloro functionality of allyldichlorosilane (HSiCl₂(C₃H₅)) and allyldichloromethylsilane (MeSiCl₂(C₃H₅)) were replaced by alkynyl groups and new compounds, allyldialkynylsilane 1 and allyldialkynylmethylsilane 2, were obtained. These silanes, which served as starting materials for the onward reactions, were purified by fractional distillation. They were further subjected to hydroboration with 9-BBN (9-borabicyclo[3.3.1]nonane) and were converted into 1-silacyclohex-2-ene derivatives 5 and 6. The competition between C≡C and C=C in the reaction was studied. The hydroborating reagent 9-BBN was expected to prefer terminal C=C bonds and to leave C≡C bond untouched. This hypothesis of preferable hydroboration was experimentally proved, and hence, 1-silacyclohex-2-ene derivatives were obtained in reasonably pure form. The reaction of allyldialkynylsilane 2 with one equivalent of 9-BBN affords 1-silacyclohex-2-ene bearing Si-C≡C-function, ready to be hydroborated further with one equivalent of 9-BBN. The obtained compound bears two C-B bonds, which are attractive synthones for further transformations. This study aims to highlight the chemistry of C-B and Si-H functional groups. All new compounds obtained were colorless air and moisture sensitive oils, and they were studied by multinuclear magnetic resonance spectroscopy (¹H, ¹³C, ¹¹B, ²⁹Si NMR) in solution.      

Synthesis and Polymerization of 2-(3-Pyrrolyl)acetic Acid Derivatives from Pyrrole

The synthesis of the 3-pyrrylacetic acid as well as the study of its esterification conditions are described. The new materials thus obtained are electropolymerized.     

Reactions of highly branched fluoroolefins with methyllithium and methylmagnesium bromide: formations of unexpected polyfluorocyclobutene and polyfluoropentadiene compounds

Introduction of a methyl group into hexafluoropropene trimers was achieved by reactions with organometallic carbon nucleophiles. Unusual cyclization and defluorination occurred simultaneously with a formation of methylated polyfluoroolefins: excess methyllithium provided a polyfluorocyclobutene compound, while a polyfluoropentadiene derivative was formed by use of excess methyllithium.     

Synthesis of 2,6-disubstituted morpholines through regioselective oxiranes ring opening by tosylamide under PTC conditions

Symmetric and non-symmetric 2,6-disubstituted morpholines were synthesized through regioselective nucleophilic ring opening of oxiranes with tosylamide under solid-liquid phase transfer catalysis (SL-PTC) conditions followed by cyclization of the tosylamido diols thus obtained and final deprotection of the corresponding N-tosyl morpholines. The morpholines prepared are interesting building blocks in the synthesis of pharmaceuticals and agrochemicals.     

Synthesis of 17α-amino-5α-androst-2-ene from epiandrosterone

17α-Amino-5ga-androst-2-ene was synthesized from epiandrosterone via formation of the tosylate followed by nucleophilic substitution by azide and reduction with LiAlH₄. The structures of the products were proved by NMR and IR spectroscopy and mass spectrometry. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 257–258, May–June, 2006.     

Synthesis of benzimidazoles from o-phenylenediamines and DMF derivatives in the presence of PhSiH3

A simple approach to preparation of benzimidazoles from o-phenylenediamines and DMF derivatives, only employing PhSiH₃ as promoter without any other additives, was reported. This route provided moderate to high yields with a broad substrate scope. A plausible mechanism for the reaction is proposed based on the spectroscopic characterization (e.g., HRMS and ¹H NMR) of the reaction mixture.     

Synthesis of N-alkoxy-substituted 2H-benzimidazoles

Treatment of 2-nitro-N-(2-methyl-1-propen-1-yl)benzenamines with potassium tert-butoxide in tert-butanol followed by the addition of an electrophile affords N-alkoxy-2H-benzimidazoles. Electrophiles including methyl iodide, allylic bromides, propargylic bromides, benzyl bromide, and acetyl chloride gave good to excellent yields of product while 1-iodo- and 2-iodo-butane afforded very low yields.