A convenient method for 3-pyrroline synthesis

[reaction: see text]. The synthesis of a range of 3-pyrrolines has been achieved from primary amine starting materials using a two-step alkylation/alkylidene carbene CH-insertion reaction sequence. We have shown that insertion into a range of CH-bond types is possible, and the formation of nitrogen-bearing quaternary stereocenters is a relatively facile process. The insertion reaction occurs with >95% retention of stereochemistry, but the presence of protecting groups on nitrogen is generally deleterious to the cyclization process.     

A convenient method for the synthesis of roflumilast

A convenient synthetic method has been developed for the synthesis of roflumilast from 4-difluoromethoxy-3-hydroxybenzaldehyde and bromomethyl cyclopropane via O-alkylation, oxidation and N-acylation. With sodium hydroxide as alkali in the last step, the total yield of roflumilast can be up to 68.3 % and the purity of the target product reached 99.2 %. It was obvious that sodium hydroxide showed more economic advantage for scale-up production than sodium hydride or potassium tert-butoxide.     

A convenient synthesis of phosphoenolpyruvate via silyl-ester intermediate

Phosphoenolpyruvate was synthesized in high yield by a simple procedure starting from pyruvic acid and dimethyl trimethylsilyl phosphite through trimethylsilylation, bromination, and the Perkow reaction.     

A new convenient method for the synthesis of cardiolipin

A novel dichlorophosphate coupling method is developed for the synthesis of the title compound. O-Chlorophenyl dichlorophosphate can be used as a mild phosphorylating reagent to effectively couple with optically active 1,2-O-diacyl-sn-glycerol and 2-O-protected glycerol to assemble cardiolipin bearing different fatty acid chains.     

A novel and convenient synthesis of 5-aryl-4-bromo-3-carboxyisoxazoles: useful intermediates for the solid-phase synthesis of 4,5-diarylisoxazoles

A novel synthesis of 5-aryl-4-bromo-3-carboxyisoxazoles employing a [3+2] cycloaddition of a nitrile N-oxide with 2-aryl-1-bromoalkynes as the key step is described. The utility of these 5-aryl-4-bromo-3-carboxyisoxazoles in the solid-phase synthesis of 4,5-diarylisoxazoles is demonstrated.     

A convenient method for the synthesis of substituted thioureas

A convenient method for the synthesis of substituted thioureas by the reaction of primary amines with molybdenum dialkyl dithiocarbamates has been developed. Primary amines on reaction with 0.5 equiv of molybdenum xanthate produce the corresponding thioureas in moderate to good yields in short times. Similar reactions with propargylamine or 2-aminoethanol produce cyclic thiaoxazolidine and oxazolidine derivatives, respectively.     

A convenient method for the synthesis of electron-rich phosphonates

Very electron-rich benzylic-type phosphonates can be prepared by treating the corresponding alcohols in triethyl phosphite with one equivalent of iodine at an appropriate temperature in a general one-pot process.     

A convenient procedure for introducing arylsulfanyl and heterylsulfanyl groups into the 5 position of the oxazole ring

Available (2-aryl-5-mesyl-1,3-oxazol-5-yl)triphenylphosphonium salts readily react with sodium thiophenolates and their heterocyclic analogs by way of substitution of the mesyl group by an arylsulfanyl or a heterylsulfanyl group. Treatment of the products with sodium hydroxide results in their mild dephosphorylation, which was used for preparative synthesis of a series of 2-aryl-5-arylsulfanyl(heterylsulfanyl)-1,3-oxazoles.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1524–1528.Original Russian Text Copyright © 2004 by Golovchenko, Brovarets, Drach.This revised version was published online in April 2005 with a corrected cover date.     

A convenient approach to an advanced intermediate for (+)-lactacystin synthesis

A fully stereoselective preparation of the advanced intermediate 24 for the synthesis of (+)-lactacystin from known 1,2:5,6-di-O-isopropylidene-α-d-gulofuranose (2), as the source of chirality, has been achieved. The C-5 methyl group was introduced via a Wittig olefination followed by Pd/C-mediated hydrogenation of the conformationally restricted alkene 11 in a highly stereoselective manner. The stereogenic tetrasubstituted carbon centre at C-3, with an amino group, was installed stereoselectively via an Overman rearrangement, which was efficiently controlled by a saccharide environment.     

A PhSeCl-mediated allylic oxidation of prenyl moiety: a convenient method for the construction of 3-isopenten-2-ol unit

A phenylselenenyl chloride (PhSeCl)-mediated allylic oxidation to give allylically rearranged alcohol has been developed. A possible mechanism for the present reaction is generation of allylic selenide from prenyl moiety via [1,3]-sigmatropic rearrangement, followed by oxidation and [2,3]-sigmatropic rearrangement to afford 3-isopenten-2-ol.     

A convenient procedure for the synthesis of allyl and benzyl ethers from alcohols and phenols

Allyl and benzyl ethers of alcohols can be prepared conveniently and in high yield with allyl and benzyl bromide in the presence of solid potassium hydroxide without use of any solvent. Phenols can be converted to allyl ethers but are inert to benzylation under above conditions.     

A simple and convenient method for the preparation of diborane from tetrabutylammonium borohydride and benzyl chloride for application in organic synthesis

Diborane is readily generated in situ at 25 °C in toluene using the Bu₄NBH₄/PhCH₂Cl and Bu₄NBH₄/I₂ reagent systems. The reagent prepared in this way is used for the reduction of carbonyl compounds and hydroboration-oxidation of olefins to obtain the corresponding alcohols in good yields.     

A convenient method for the synthesis of N-hydroxyureas

Treatment of amines with 1-(4-nitrophenol)-N-(O-benzylhydroxy)carbamate yields the O-benzyl protected N-hydroxyureas. Hydrogenation of the O-benzyl protected N-hydroxyureas over 5% Pd/BaSO₄ cleanly gives the N-hydroxyureas in good yield. In addition to primary and secondary aliphatic and aromatic amines, this method converts amino sugars to the corresponding N-hydroxyureas without extensive protecting group chemistry.     

A convenient method for the synthesis of α-silylacetic acids

A method is described for the preparation of α-silylacetic acids of the type R₃SiCH₂CO₂H by treating trimethylsilyl acetate with LDA followed by quenching with chlorosilanes.     

A convenient method for the synthesis of six-membered heterocyclic enaminones

Enaminones are widely employed in the synthesis of heterocycles, however heterocyclic enaminones and their use in the synthesis of more complex systems have been less studied. The reaction between 4-chloroacetylacetate and aliphatic or aromatic 1,2-aminoalcohols, 1,2-aminothiols or 1,2-diamines, yields in one pot a six-membered 1,4-heterocyclic system containing the enaminone moiety.     

A convenient method for the synthesis of polyfluorinated β-diimines

The higher internal perfluoroak-2-enes react with ammonium hydroxide at atmospheric pressure to give the corresponding iminoenamines, whose further transformations yield heptafluoroacetylacetone analogs. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1710–1712, September, 1999.     

A convenient method for the synthesis of chlorocymantrene and bromocymantrene

Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2046–2047, November, 1994.     

A convenient general method for the synthesis of hydroxy diacids

Olefinic aldehydes and epoxides with terminal double bonds react with Grignard reagents, and the acetates made from the resulting alcohols undergo double bond cleavage on treatment with RuCl₃·xH₂O in the presence of NaIO₄ to give acetoxy diacids. Hydrolysis with LiOH then affords hydroxy diacids.