Bis‐Bromine‐1,4‐Diazabicyclo[2.2.2]Octane (Br2‐DABCO) as an Efficient Promoter for One‐Pot Conversion of N‐Arylglycines to N‐Arylsydnones in the Presence of NaNO2/Ac2O Under Neutral Conditions

Bis‐Bromin‐1,4‐diazabicyclo[2.2.2]octane (Br₂‐DABCO)‐promoted one‐pot conversion of various N‐arylglycines to sydnones using a combination of NaNO₂ and Ac₂O has been achieved efficiently through N‐nitrosation followed by cyclization in high yields (90‐96%) under mild and neutral conditions.     

A one-pot synthesis of a branched tertiary phosphine oxide from red phosphorus and 1-(tert-butyl)-4-vinylbenzene in KOH-DMSO: an unusually facile addition of P-centered nucleophiles to a weakly electrophilic double bond

Red phosphorus reacts with 1-(tert-butyl)-4-vinylbenzene in a superbase media (KOH-DMSO, 90-100 °C, 3 h) to give tris[4-(tert-butyl)phenethyl]phosphine oxide in 77% yield. Microwave activation of the reaction affords the phosphine oxide in 82% yield in 6 min.     

Polyethylene glycol (PEG-400): an efficient green reaction medium for the synthesis of benzo[4,5]imidazo[1,2-a]-pyrimido[4,5-d]pyrimidin-4(1H)-ones under catalyst-free conditions

A simple and an efficient eco-friendly methodology has been developed for the synthesis of benzo[4,5]imidazo[1,2-a]-pyrimido[4,5-d]pyrimidin-4(1H)-ones in excellent yields under catalyst-free-conditions using inexpensive and non-toxic polyethylene glycol (PEG-400) medium. This new protocol offers an environmental acceptability, shorter reaction time, room temperature, low cost, high yields, and recyclability of the PEG-400 medium are the important features. This method provides a green and much improved protocol over the existing methods.     

Reaction of diketene with cyanothioacetamide: A convenient and regioselective method for the preparation of new 4(1H)-pyridone derivatives

The reaction of diketene with cyanothioacetamide in dry dioxane in the presence of triethylamine gives triethylammonium 3-cyano-6-methyl-4-oxo-1,4-dihydro-2-pyridinethiolate. The regioselective S-alkylation of this thiolate is a convenient method for the preparation of substituted 4(1H)-pyridones and also derivatives of thiazolo[3,2-a]pyridine and thieno[2,3-b]pyridine. The action of 2-amino-1,1,3-tricyanopropene on this thiolate leads to its transformation into a new heterocyclic system, namely, 5H-pyrido[2′,3′:4,5]thiopyrano[2,3-b]pyridine; treatment with iodine yields the oxidation product, namely, the corresponding bis(2-pyridyl) disulfide. The structure of isopropyl (3-cyano-6-methyl-4-oxo-1,4-dihydro-2-pyridinyl)thioacetate was confirmed by X-ray diffraction structural analysis. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 716–725, May, 2007.     

AlCl3-mediated tandem Friedel-Crafts reactions of vinylidenecyclopropanes with acyl chlorides: a facile synthetic method for the construction of 1-[2-(2,2-diarylvinyl)-1-phenyl-3H-inden-5-yl]ethanone derivatives

AlCl₃-mediated tandem Friedel-Crafts reaction of vinylidenecyclopropanes with acyl chlorides produced the corresponding 1-[2-(2,2-diarylvinyl)-1-phenyl-3H-inden-5-yl]ethanone derivatives in moderate to good yields under mild conditions within short reaction time.     

Nucleophilic substitution at phosphorus: stereochemistry and mechanisms

This review is devoted to the stereochemistry of nucleophilic substitution reactions at phosphorus. The study of the reactions of phosphoryl group transfer is important for biological and molecular chemistry. The stereochemistry and mechanisms of S_N1(P) monomolecular and S_N2(P) bimolecular nucleophilic substitution reactions of organophosphorus compounds are discussed. It has been shown that hydrolysis of many natural phosphates proceeds according to the monomolecular S_N1(P) mechanism via the formation of metaphosphate intermediate (PO₃^?). S_N2(P) nucleophilic substitution at chiral trivalent or pentavalent phosphorus compounds proceeds via the formation of penta-coordinated transition state or pentacoordinate intermediate.     

Asymmetric catalysis as a method for the synthesis of chiral organophosphorus compounds

This review discusses methods for the metallo-, organo- and biocatalytic asymmetric synthesis of chiral organophosphorus compounds with many applications in stereoselective synthesis with references to updated literature reports as well as the author’s original research. Asymmetric catalytic hydrogenation and reduction with chiral organometallic complexes, together with actively used asymmetric organocatalytic versions of various reactions enable us to synthesize chiral organophosphonates and phosphinates with high enantioselectivity and purity. Asymmetric catalysis is also an effective tool to realize some classic reactions of phosphorus chemistry in a stereospecific manner.