Synthesis of dihydrofuro[2,3‐b]pyridines by the reaction of 2‐amino‐4,5‐dihydro‐3‐furancarbonitriles with α,β‐unsaturated carbonyl compounds

The reactions of 2‐amino‐4,5‐dihydro‐3‐furancarbonitriles 1a‐d with α,β‐unsaturated carbonyl compounds in the presence of sodium ethoxide (0.1 equivalent) gave the corresponding Michael adducts 2a‐d , 3a‐d and 4a‐d. Compounds 2a‐d and 3a‐c reacted with sodium alkoxide (1 equivalent) to yield the corresponding 7a‐alkoxyhexahydrofuro[2,3‐b]pyridines 5a‐d, 6a‐d, 7a‐c and 8a‐c . Treatment of 5a‐d, 6a‐d, 7a‐c and 8a‐c with potassium tert‐butoxide produced the corresponding dihydrofuro[2,3‐b]pyridines 9a‐d and 10a‐c . The reaction of 4a‐c with sodium ethoxide (1 equivalent) afforded the corresponding dihydro‐furo[2,3‐b]pyridines 11a‐c .     

Hydrogen‐transfer reduction of α,β‐unsaturated carbonyl compounds catalyzed by naphthyridine‐functionalized N‐heterocyclic carbene complexes

Substitution of silver complex of 2‐chloro‐7‐(mesitylimidazolylidenylmethyl)naphthyridine (NpNHC) with palladium(II), rhodium(I) and iridium(I) metal precursors provided [Pd(C ,N ‐NpNHC)(η³‐allyl)](BF₄) ( 5 ), RhCl(COD)(C ‐NpNHC) ( 6a ) and IrCl(COD)(C ‐NpNHC) ( 6b ), respectively. Abstraction of chloride from 6a and 6b with AgBF₄ provided the chelation complexes [Rh(COD)(C ,N ‐NpNHC)](BF₄) ( 7a ) and Ir(COD)(C ,N ‐NpNHC)(BF₄) ( 7b ), respectively. All complexes were characterized using NMR and elemental analyses and the structural details of 5 and 6a were further confirmed using X‐ray crystallography. In catalytic activity studies, complex 5 was found to be an effective catalyst in the hydrogen‐transfer reduction of α,β‐unsaturated carbonyl compounds into the corresponding saturated carbonyl compounds.     

Torsion angle relationship of the 17O NMR chemical shift in α,β‐unsaturated carbonyl compounds

The torsion angle effect on the isotropic shielding of ¹⁷O nucleus in α,β‐unsaturated carbonyl groups is studied by means of density functional theory (DFT) calculations using a polarizable continuum model (PCM) for the solvent, employing the PBE0 functional together with the 6‐311G(d,p) basis set for geometry optimization, and the 6‐311+G(2d,p) basis set for calculating the NMR shielding with the gauge‐including atomic orbitals (GIAO) method. This study adds new information on the sensitivity of the ¹⁷O nucleus to conformational changes, revealing a strong dependence of the ¹⁷O NMR chemical shift on the dihedral angle between the carbonyl and the vinyl moiety in all studied compounds; remarkable differences are observed with the data reported for α‐diketones. Copyright © 2009 John Wiley & Sons, Ltd.     

Use of Ph3P=N‐Li: Synthesis of α,β‐unsaturated nitriles from α,β‐unsaturated esters via the formation of N‐(α,β‐unsaturated acyl) phosphinimines

The reaction of Ph₃P=NLi with various α,β‐unsaturated esters gives access to new N‐(α,β‐unsaturated acyl) phosphinimines, which can undergo intramolecular aza‐Wittig reactions (at 65–110°C) to afford the corresponding nitriles. The structures of all new compounds were established by elementary analyses, IR, ¹H‐, ¹³C‐, and ³¹P‐NMR spectroscopy. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 49–54, 1999     

Reactions of 3‐methylamino‐5‐phenylthiophene with α,β‐unsaturated esters and α,β‐unsaturated nitriles

Treatment of 3‐methylamino‐5‐phenylthiophene with α,β‐unsaturated esters, i.e., methyl acrylate, (E)‐methyl crotonate, diethyl fumarate, diethyl maleate and ethyl propiolate, in tetrahydrofuran for several days at reflux gave 1‐methyl‐3,4‐dihydrothieno[2,3‐e]pyridin‐2‐ones 4 and/or 1‐methylthieno[2,3‐e]pyridin‐2‐ones 5 , depending on the structure of the esters. On the other hand, the same reactions with α,β‐unsaturated nitriles such as acrylonitrile and tetracyanoethene, gave the corresponding thiophenes 7 and 10 bearing 2‐cyanoethyl and 1,2,2‐tricyanoethenyl groups at C‐2, respectively. The reaction with (Z)‐1,2‐dicyanoethene under the same conditions produced the corresponding thiophene 9 bearing the 1,2‐dicyanoethenyl group and 1,2‐dicyano‐5‐methylaminobiphenyl.     

Reduction of α,β unsaturated carbonyl compounds by Ni–BH4

The reduction of α,β unsaturated carbonyl compounds by sodiumborohydride is catalysed by Ni(bpy)Cl₂ (bpy=2,2′-bipyridine). Various carbonyl compounds having the general formula R₁CH=CHCRO [where R₁, R=C₆H₅, H; p-MeO---C₆H₄---,C₆H₄; p-CH₃---C₆H₄, C₆H₅; (m-OMe---)(p-OMe---)C₆H₃, C₆H₅; C₆H₅, (CH₃)₂CH---; CH₃, H; m-Br---C₆H₄---, C₆H₅] are reduced to corresponding allylicalcohol [R₁CH=CHCRHOH] at 25°C within half an hour. During these reductions the double bond is partially reduced to give saturated alcohols as minor products having the molecular formula R₁CH₂CH₂CRHOH. The reduction of trans-3-phenyl-2-propenal with NaBH₄ and catalytic amounts of Ni(bpy)Cl₂ in solvents containing active deuterium (D₂O, CD₃OD), leads to the partial incorporation of deuterium at the α and γ positions to give C---D bonded alcohols.     

Reactions of 4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidines with α,β‐unsaturated carbonyl compounds

The reaction of 5,7‐diphenyl‐4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidine ( 1 ) with α,β‐unsaturated carbonyl compounds 2a‐f led to the formation of the alkylated heterocycles 3a‐f (Figure 1). However, the reaction of 5‐methyl‐7‐phenyl‐4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidine ( 5 ) with 2a‐c yielded under the same conditions the triazolo[5,1‐b]quinazolines 6a‐c (Figure 3). In this case, the alkylation is followed by a cyclocondensation. The structure elucidation of the products is based on ir, ms, ¹H and ¹³C nmr measurements and on an X‐ray diffraction study.     

Δ2‐Isoxazolines from β,γ‐unsaturated oximes

3,5‐Disubstituted Δ²‐isoxazolines can be prepared using the palladium‐mediated nucleometalation / methoxycarbonylation of β,γ‐unsaturated oximes. This novel route to this class of compounds is tolerant of a wide variety of functionality in the starting material, and provides a rapid route to highly functionalized isoxazolines.     

5-雄烯-3β, 7α, 17β-三醇和5-雄烯-3β, 7β, 17β-三醇的合成

以5-雄烯二醇为原料,用微生物转化的方法合成了两个重要的神经甾体5-雄烯-3β, 7α, 17β-三醇和5-雄烯-3β, 7β, 17β-三醇。所用菌种总枝毛霉为我们自己筛选,并首次应用于5-雄烯-3β, 7α, 17β-三醇和5-雄烯-3β, 7β, 17β-三醇的合成中。     

Synthesis of β‐monosubstituted α,β‐unsaturated amides with Z‐selectivity using diphenylphosphonoacetamides

The utility of diphenylphosphonoacetamides [(PhO)₂P(O)CH₂CONRR′] as Horner–Wadsworth–Emmons reagents was examined with five different patterns of substitution upon the amide nitrogen atom ( 2a : R, R′ = CH₂Ph; 2b : R = CH₂Ph, R′ = H; 2c : R = Me, R′ = OMe; 2d : R, R′ = Ph; 2e : R, R′ = (CH₂)₄). The reaction of 2a was found to be Z‐selective for aromatic aldehydes with selectivities up to 95:5. Reagent 2b led to reasonable selectivity for both benzaldehyde (85:15) and 3‐phenylpropionaldehyde (87:13), while 2c was somewhat effective for only the latter alkyl aldehyde (83:17). Compounds 2d and 2e exhibited slightly lower selectivities compared with 2a . © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:515–523, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20054     

Michael addition of dimedone with α,β‐unsaturated ketones: Synthesis of quinoline and chromene derivatives

A series of quinoline and chromene derivatives has been synthesized by Michael addition of dimedone 1 with 2‐aroyl‐3‐arylacrylonitrile 2 and study of absorption and fluorescence maxima of quinolines.     

Synthesis of 1‐substituted 3,5‐diaryl‐2‐pyrazolines by the reaction of α,β‐unsaturated ketones with hydrazines

1‐Acetyl‐, 1‐propionyl‐ and 1‐phenyl‐3,5‐diaryl‐2‐pyrazolines have been synthesized by the reaction of the appropriate α,β‐unsaturated ketones with hydrazine or phenylhydrazine in hot acetic acid or propionic acid. Structures of all new 2‐pyrazolines 16‐40 have been elucidated by microanalyses, ¹H and ¹³C nmr spectroscopies.     

Research on heterocyclic compounds. XLIII. Synthetic studies on 1,4‐dihydropyridine derivatives

In order to obtain N‐benzyl‐3,5‐dicarbethoxy‐2,6‐dimethyl‐4‐phenyl‐1,4‐dihydropyridine 1 as a lead compound of pharmacological interest, the classical Hantzsch synthetic method and the modified Collie procedure were used. However, only a very low yield of 1 was obtained in a mixture with larger amounts of some by‐products ( 2, 3, 4 ). Compound 1 was then synthesized in satisfactory yield via a different method, together with another by‐product ( 9 ). The structures of all by‐products were elucidated and possible mechanisms leading to the formation of such compounds are described.