Synthesis of new polysubstituted (pyrazoles, pyrimidines and quinolines) five and six-membered heterocycles: reaction of α,α-dioxoketene dithioacetals with nucleophiles

A novel synthesis of polysubstituted pyrazoles 3a-d, pyrimidines 4a-f and quinolines 5a-c via the reaction of α,α-oxoketene dithioacetals 2a-c with hydrazine hydrate, malonohydrazide, urea, thiourea and aniline is reported and the synthetic potential of the method is demonstrated. The structure of the new compounds was established upon their elemental analysis, IR, ¹H NMR and ¹³C NMR.     

Convenient Method for the Friedel–Crafts Acylation of Benzene Derivatives Using Silver Nitrate as Catalyst

Friedel–Crafts acylation of benzene derivatives such as anisole, toluene, and xylene has been successively carried out using silver nitrate as the catalyst in the presence of an eco friendly solvent (ethyl alcohol). Both benzoyl chloride and acetyl chloride reacted smoothly under the conditions to afford the corresponding ketones in good yield.

Mercuric Acetate in Organic Synthesis: A Simple Procedure for the Synthesis of Pyrazolines1

Reaction of aldehyde hydrazones (1) with mercuric acetate leads to the formation of nitrile imines (2) which can react insitu with olefins to produce 1,3,5-trisubstituted 2-pyrazolines (4) in good yield.     

An alternative total synthesis of Patulolide A

A new total synthesis of [R]‐Patulolide A from readily available (R)‐propylene epoxide obtained using the asymmetric synthetic approach is reported. The key reactions involved are ozonolysis and Yamaguchi macrolactonization, resulting in the ring system.     

Crystal structure of bis(2-butyl-4-chloro-imidazole)5-iminoethane

The title compound (C₁₈H₂₆N₆Cl₂) crystallizes in monoclinic space group P2₁/c with a = 14.867(4) Å}, b = 7.758(2) Å}, c = 9.671(3) Å}, = 108.78(1), V = 1056.0(5) Å}³, Z = 2, D_cal = 1.250 Mg/m³ at T = 293 K. The structure was solved by direct methods and refined by full-matrix least-squares procedures to final R = 0.0650 and wR = 0.1719 using 2493 reflections. The imidazole ring is planar and the n-butyl chain adopts an extended conformation. The molecules in the crystal are stabilized by N–H s N type of intermolecular hydrogen bondings in addition to van der Waals forces.     

A new method for the generation of α‐nitrosoolefins from ketooximes and its application to the synthesis of 5,6‐dihydro‐4H‐1,2‐oxazine derivatives

Reaction of ketooximes containing α‐methylene group with chloramine‐T followed by treatment with tri‐ethylamine leads to the formation of α‐nitrosoolefins via α‐nitrosochloride, which can react in situ intermol‐ecularly with olefinic compounds to produce 5,6‐dihydro‐4H‐1,2‐oxazine derivatives in good yield.     

Stereoselective Formation of Functionalized 2-Aryl-tetrahydrofurans from Aromatic Aldehydes via Intramolecular 1,3-Dipolar Cycloadditions (INOC and IOOC)

α-Allyloxyaldoximes 8, formed by the reduction of β-nitrostyrenes 5 with SnCl₂-2H₂O in the presence of an unsaturated alcohol, undergo either thermally induced intramolecular oxime olefin cycloaddition (IOOC) to bicyclic isoxazolidines 7, with stereospecific introduction of three stereocenters, or nitrile oxide olefin cycloadditions (INOC) to bicyclic isoxazolines 6. This provides an entry into functionalized tetrahydrofurans and tetrahydropyrans.     

Chemo‐ and regioselective allylic oxidation: Oxo‐derivatives of 2‐phospholene sugar analogs

A convenient and facile chemo‐ and regioselective oxidation of the allylic methylene group in a 2‐phospholene ring system afforded the novel carbonyl derivatives of 2‐phospholenes ( 2a–i ). The method gives high conversion and selectivity in the formation of allylic ketones. The advantages of this oxidation method in such a five‐membered pseudo sugar 2‐phospholene ring are mentioned, and the oxidation is examined on several substituted 2‐phospholenes ( 1a–i ). © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:320–325, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10154