The Synthesis of Fluorine Containing Polysiloxanes. Part 1. The Synthesis of Fluorine Containing Cyclosiloxanes

A new facile preparative method for the synthesis of semifluorinated organocyclosiloxanes is reported. Ring closure of the dichlorosilanes with NaHCO₃ and pyridine gave a mixture of semifluorinated organocyclosiloxanes with cyclotrisiloxane as the main product in yields 95–98% with yield of cyclotrisiloxanes up to 80%.     

Efficient One‐Pot Synthesis of Hydroxyflavanones by Cyclization and O‐Demethylation of Methoxychalcones

An efficient one‐pot method for the synthesis of hydroxyflavanones is described. Methoxychalcones are treated with 36% HBr to afford cyclization and regioselective O‐demethylation products (2a–i) while cyclization and complete O‐demethylation products (3a–e) are obtained in the presence of 45% HI.     

Diastereoselective Synthesis of Enantiopure α-Aminophosphonic Acid Derivatives: Pudovik Reaction in Stereoselective Synthesis (Dedicated to A. N. Pudovik, 1916–2006)

In this report, we present the application of Pudovik reaction in the synthesis of chiral organophosphorus compounds and shown this reaction to be a promising way to enantiopure aminophosphonic acid derivatives. Cyclization reactions are a new, most efficient strategy for stereoselective synthesis of α-aminophosphonates, namely an intramolecular type of interaction of the P(III) atom and an imino group.     

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 .     

Application of Sulfinyl bis(2,4‐dihydroxythiobenzoyl) in the Synthesis of N‐Substituted 2‐Amino‐5‐(2,4‐dihydroxyphenyl)‐1,3,4‐thiadiazoles

One‐stage synthesis of N‐substituted 2‐amino‐5‐(2,4‐dihydroxyphenyl)‐1,3,4‐thiadiazoles is described. The compounds were prepared by the reaction of the sulfinyl bis(2,4‐dihydroxythiobenzoyl) (STB) with 4‐substituted 3‐thiosemicarbazides. STB was obtained from 2,4‐dihydroxybenzenecarbodithioic acid and thionyl dichloride. The structure of compounds was confirmed by IR, ¹H NMR, ¹³C NMR, and EI‐MS data.     

Convenient Synthesis of 6-Bromo-1,2,3,4-tetrahydroisoquinoline and 3-Methoxy-1,2,3,4-tetrahydro-[2,7]-naphthyridine via Reductive Amination of Schiff's Bases

Synthesis of 7-bromo-1,2,3,4-tetrahydroisoquinoline and 6-methoxy-1,2,3,4-tetrahydro-[2,7]-naphthyridine via lithiation of 2-methylarylidene-tert-butylamines, followed by formylation, reductive amination in one-pot, and removal of the tert-butyl group from the nitrogen, is described.     

New Route to Synthesis of Unexpected Pyridoin Derivatives: Their Structure Determination with Spectroscopic and X-Ray Methods

The new 1,2,4-triazine-3-thione derivatives were obtained by a new route using a one-step process. The structure of the compounds was determined with infrared (IR), ¹H NMR, and ¹³C NMR spectroscopic methods and elemental analysis. A representative x-ray crystallographic analysis of 3 was given, and its x-ray data are discussed in detail. This is a facile procedure and shorter than earlier methods.     

New Synthetic Approaches to Naturally Occurring and Unnatural Pyranoflavones

Total synthesis of biologically interesting natural and unnatural pyranoflavones has been accomplished starting from readily available 2,4‐dihydroxyacetophenone or 2,4‐dihydroxy‐6‐methoxyacetophenone in three steps, i.e., benzopyran formation, condensation, and cyclization reaction.     

Regioselective Synthesis of Trichloromethyl‐Substituted Salicylates and Cyclohexenones by One‐Pot Cyclizations of 1,3‐Bis(trimethylsilyloxy)buta‐1,3‐dienes

A variety of 6‐(trichloromethyl)salicylates (=2‐hydroxy‐6‐(trichloromethyl)benzoates) were prepared by TiCl₄‐mediated cyclization of 1,3‐bis(trimethylsilyloxy)buta‐1,3‐dienes with 1,1,1‐trichloro‐4,4‐dimethoxybut‐3‐en‐2‐one. The employment of trimethylsilyl trifluoromethanesulfonate (Me₃SiOTf) as Lewis acid resulted in the formation of trichloromethyl‐substituted cyclohexenones. The cyclizations proceeded with good‐to‐very‐good regioselectivities.     

Ionic Liquid–Mediated One-Pot Synthesis of 5-(Trifluoromethyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine Derivatives

A facile one-pot synthesis of 5-(trifluoromethyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine derivatives is described via a three-component reaction of aldehydes with 5-aminotetrazole and ethyl 4,4,4-trifluoro-3-oxobutanoate or 4,4,4-trifluoro-1-phenylbutane-1,3-dione in ionic liquid. This method has the advantages of short synthetic route, operational simplicities, good yields, ecofriendliness, and recyclability of the solvent.