Efficient synthesis of 4-(3'-furanyl)butenolide derivatives via PdII-catalyzed oxidative heterodimeric cyclization reaction of 2,3-allenoic acids and 1,2-allenyl ketones

The oxidative cyclization/dimerization reaction between two classes of allenes with different functionalities was reported to provide an efficient route to polysubstituted 4-(3'-furanyl)-2(5H)-furanones, which are not readily available from the known methods. The highly optically active butenolides could be easily formed from the optically active 2,3-allenoic acids, which was obtained conveniently through chiral resolution with optically active amines, that is, cinchonidine or alpha-methyl benzylamine. A mechanistic study showed that the reaction proceeded via a matched double oxypalladation-reductive elimination process. The Pd(II) species may be regenerated via the subsequent cyclometallation of two equivalents of 1,2-allenyl ketones with Pd(0) and protonlysis of Pd enolates formed with the in situ generated HCl.     

K(2)CO(3)-catalyzed Michael addition-lactonization reaction of 1,2-allenyl ketones with electron-withdrawing group substituted acetates. An efficient synthesis of alpha-pyrone derivatives

[reaction: see text] Alpha-pyrone derivatives were synthesized via the base catalyzed or promoted reaction of 1,2-allenyl ketones and electron-withdrawing group substituted acetates. The reaction was believed to proceed through a Michael addition C-C double-bond migration-lactonization process.     

PdCl2-catalyzed two-component cross-coupling cyclization of 2,3-allenoic acids with 2,3-allenols. An efficient synthesis of 4-(1',3'-dien-2'-yl)-2(5H)-furanone derivatives

Cross-coupling cyclization reaction between 2,3-allenoic acids 1 and 2,3-allenols 2, in which two allenes functioned differently, was realized to afford 4-(1',3'-dien-2'-yl)-2(5H)-furanone derivatives 3. The reaction may proceed via an oxypalladation, insertion, and beta-hydroxide elimination process. A high E-stereoselectivity of the new formed C=C double bond was observed.     

PdI2-catalyzed coupling-cyclization reactions involving two different 2,3-allenols: an efficient synthesis of 4-(1',3'-dien-2'-yl)-2,5-dihydrofuran derivatives

Transition-metal-catalyzed dimeric coupling-cyclization reactions of two different 2,3-allenols afforded 4-(1',3'-dien-2'-yl)-2,5-dihydrofuran derivatives 3. 2-Substituted 2,3-allenols 1 cyclized to form the 2,5-dihydrofuran ring, whereas the 2-unsubstituted 2,3-allenols 2 provided the 1,3-diene unit at the 4-position. The reaction is proposed to proceed through an oxypalladation, insertion, and beta-hydroxide elimination process. The C=C double bond was formed with high E stereoselectivity by beta-hydroxide elimination.     

Pd(II)-catalyzed oxidative dimeric cyclization-coupling reaction of 2,3-allenoic acids: an efficient synthesis of bibutenolide derivatives

Three sets of convenient catalytic systems have been developed for the oxidative dimeric cyclization coupling of differently substituted 2,3-allenoic acids catalyzed by Pd(II), affording bibutenolides that are not otherwise readily available. The advantages and disadvantages of these systems are discussed. Although the diastereoselectivity for the bicyclization of racemic 2,3-allenoic acids is low, excellent diastereoselectivity was realized in the bicyclization reaction of optically active 2,3-allenoic acids, leading to the optically active bibutenolides in high yields and ee. Based on a mechanistic study, it is believed that the reaction may proceed by means of a double oxypalladation and reductive elimination to yield butenolide 3 and Pd(0) species, which may be reoxidized to the catalytically active Pd(II) species in the presence of alkyl iodide/air, metallic iodide/air, or benzoquinone.     

Steric hindrance-controlled Pd(0)-catalyzed coupling-cyclization of 2,3-allenamides and organic iodides. An efficient synthesis of iminolactones and gamma-hydroxy-gamma-lactams

Under the catalysis of 1 mol % Pd(PPh3)4, the reaction of 4,4-disubstituted 2,3-allenamides and organic iodides in toluene afforded iminolactones stereospecifically in >90% yields using K2CO3 (2 equiv)-5 mol % TBAB as the base. A similar reaction with 4-monosubstituted 2,3-allenamides afforded gamma-hydroxy-gamma-lactams in relatively lower yields. The N/O-attack selectivity may be determined by the steric effect at the 4-position of 2,3-allenamides.     

Palladium acetate-catalyzed cyclization reaction of 2,3-allenoic acids in the presence of simple allenes: an efficient synthesis of 4-(1'-bromoalk-2'(Z)-en-2'-yl)furan-2(5H)-one derivatives and the synthetic application

We have realized a cyclization reaction of 2,3-allenoic acids 1 in the presence of simple alkyl- or aryl-substituted allenes 3. In this reaction, the cyclic oxypalladation of 2,3-allenoic acid with Pd(II) would afford the furanonyl palladium intermediate 2, which could be trapped by the simple allene to afford a pi-allylic intermediate anti-9. This intermediate anti-9 could be nucleophilically attacked by Br- to yield 4-(1'-bromoalk-2'(Z)-en-2'-yl)furan-2(5H)-one derivatives Z-5 and Pd(0). The in-situ formed Pd(0) was efficiently converted to the catalytically active Pd(II) species by benzoquinone in HOAc. The functional groups, such as malonate, acetoxyl, and phthalic amide in allene 3, are tolerable under the current conditions. High efficiency of chirality transfer was observed when optically active 2,3-allenoic acids were used, which reveals that the formation of the intermediates 2 was a highly stereoselective anti-oxypalladation process. The highly selective formation of Z-isomer may be explained by face-selective coordination of allene 3 with the palladium atom in intermediate 2: the palladium atom coordinates to the terminal C=C double bond of allene 3 from the face opposite to the substituent group to avoid the steric congestion. The products Z-5 could be further elaborated via the S(N)2 nucleophilic substitution with amine or sodium benzenesulfinate, the reduction of the C-Br bond by NaBH(4), and the CuBr.SMe(2)-catalyzed S(N)2'-substitution with CH(3)MgBr.     

4-Methyl-1,2,3,5-dithiadiazoliumsalze Die Kristallstrukturen von (CH3CN2S2)5[CoCl4]Cl3 und (CH3CN2S2)Cl

4-Methyl-1,2,3,5-dithiadiazolium Salts. Crystal Structures of(CH₃CN₂S₂)₅[CoCl₄]Cl₃ and (CH₃CN₂S₂)Cl 4-Methyl-1,2,3,5-dithiadiazolium tetrachlorocobaltate trichloride, (CH₃CN₂S₂)₅[CoCl₄]Cl₃, was obtained by reaction of trithiazyl chloride, (NSCl)₃, with CoCl₂ in acetonitrile; it forms brown, moisture sensitive crystals. With tetraphenylarsonium chloride in CH₂Cl₂ it yields yellow crystalline (CH₃CN₂S₂)Cl and (AsPh₄)₂CoCl₄. The IR spectra of the title compounds are reported and assigned. Theit crystal structures were determined by X-ray diffraction. Crystal data: (CH₃CN₂S₂)₅[CoCl₄]Cl₃, orthorhombic, P2₁2₁2₁, Z = 4, a = 830, b = 1603, c = 2443 pm at 180 K (structure determination with 1787 observed independent reflexions, R = 0.070); (CH₃CN₂S₂)Cl, triclinic, P2₁2₁2₁, Z = 4, a = 749, b = 819, c = 1015 pm, α = 84.9, β = 67.4, γ = 84.6° at 296 K (2653 reflexions, R = 0.040). Both compounds are ionic, having chloride and distorted tetrahedral CoCl₄^2? anions and planar 4-methyl-1,2,3,5-dithiadiazolium cations which nearly fulfill C_2v symmetry. The (CH₃CN₂S₂)₅[CoCl₄]Cl₃ structure contains five symmetry independent cations, (CH₃CN₂Cl has two symmetry independent cations, all being nearly equal. No nitrogen atom but all sulfur atoms of the cations have contact with three to five chlorine atoms, and as a rule there is one chloride ion which is coplanar with the cation and exhibits rather short distances to both S atoms (288 to 309 pm); therefore, the positive charge of the cations must be concentrated on the sulfur atoms.     

Unexpected facile sequential halolactamization-hydroxylation of 2, 3-allenamides with CuX(2) for the efficient synthesis of 4-halo-5-hydroxypyrrol-2(5H)-ones

[reaction: see text] 4-Halo-5-hydroxypyrrol-2(5H)-ones were synthesized from the efficient sequential halolactamization-hydroxylation reaction of 4-monosubstituted 2,3-allenamides with CuX(2) (X = Br, Cl) in high yields. Halolactamization of fully substituted 2,3-dienamide (1f) afforded 4-halo-pyrrol-2(5H)-ones.     

Synthesis and E/Z configuration determination of novel derivatives of 3-aryl-2-(benzothiazol-2'-ylthio) acrylonitrile, 3-(benzothiazol-2'-ylthio)-4-(furan-2'-yl)-3-buten-2-one and 2-(1-(furan-2'-yl)-3'-oxobut-1'-en-2-ylthio)-3-phenylquinazolin-4(3H)-one

Knoevenagel condensation of 2-(benzothiazol-2-ylthio) acetonitrile (2) with either furan-2-carbaldehyde or thiophene-2-carbaldehydes leads to E-isomers 4a-b exclusively, while the condensation of the compound 2 with benzaldehyde or para-substituted benzaldehydes with an electron-donating group afforded E/Z mixtures 4c-e with preferentially formation of the E-isomer. Condensation of furan-2-carbaldehyde (3a) with either 1-(benzothiazol-2'-ylthio) propan-2-one (5) or 2-(2'-oxo propylthio)-3-phenyl-quinazolin-4(3H)-one (9) leads exclusively to the Z-isomers of 6 and 10, respectively. The structures of the newly synthesized compounds were elucidated by elemental analyses, 1H-NMR and 13C-NMR spectra, COSY, HSQC, HMBC, NOE, MS and X-ray crystallographic investigations.     

Attempted Abstraction of the Halogenides in (HNEt3)[Re(CH3CN)2Cl4] and Crystal Structures of cis‐[Re(CH3CN)2Cl4]·CH3CN and cis‐[Re(NHC(OCH3)CH3)2Cl4]

The abstraction of the halogenide ligands in [Re(CH₃CN)₂Cl₄]^? should result in a solvent‐only stabilized Re^III complex. The reactions of salts of [Re(CH₃CN)₂Cl₄]^? with silver(I) and thallium(I) salts were investigated and the solid‐state structures of cis‐[Re(CH₃CN)₂Cl₄]·CH₃CN and cis‐[Re(NHC(OCH₃)CH₃)₂Cl₄] are described.     

PdCl2/NaI-catalyzed homodimeric coupling-cyclization reaction of 2,3-allenols: an efficient synthesis of 4-(1',3'-dien-2'-yl)-2,5-dihydrofuran derivatives

A PdCl2/NaI-catalyzed homodimeric coupling-cyclization reaction of 2,3-allenols was observed to provide an efficient route to 4-(1',3'-dien-2'-yl)-2,5-dihydrofuran derivatives. By using the easily available optically active starting materials, 2,5-dihydrofurans with high enantiopurity may be prepared. A Pd(II)-catalyzed mechanism was also discussed.     

Syntheses, Spectroscopic Properties and Crystal Structures of （2-Cl-C6H4CH2）3SnS2CN（C5H10） and （2-Cl-C6H4CH2）3SnS2CN（C4H9N）

1 INTRODUCTION The chemistry of organotin(IV) complexes was extensively studied due to their biological activity and coordination chemistry[1～7]. More recently, phar- maceutical properties of alkyltin(IV) complexes with dithiocarbamate ligands have bee…     

Chemoselective synthesis of highly substituted 1,2-allenyl ketones, furans, and 2-alkynyl ketones from reaction of lithium selenolates with 1-(1-alkynyl)cyclopropyl ketones and electrophiles

A homo-Michael addition reaction of lithium selenolates with 1-(1-alkynyl)cyclopropyl ketones and the subsequent reaction with electrophiles such as PhSeBr, NFSI and NCS is reported. Based on the nature of electrophiles, this reaction may afford highly substituted 1,2-allenyl ketones or furans (E(+) = PhSe(+)) and 2-alkynyl ketones (E(+) = F(+), Cl(+), active halides) as the final products, respectively.     

ZnO nanoparticle-catalyzed efficient one-pot three-component synthesis of 3,4,5-trisubstituted furan-2(5H)-ones

An efficient and high-yielding protocol using nano-ZnO (50–100 nm) as an efficient heterogeneous catalyst for one-pot three-component synthesis of pharmacologically significant furanone derivatives by the condensation of aromatic aldehyde, amine and dimethylacetylenedicarboxylate has been developed. Since the catalyst is heterogeneous, it can be easily separated and recycled several times without much loss of its catalytic activity. Use of aqueous medium, recyclable nanocatalyst, operational simplicity, non-chromatographic purification technique, excellent yield and short reaction time makes this approach an attractive protocol for the synthesis of 3,4,5-trisubstituted furan-2(5H)-ones.     

Pd0-catalyzed coupling cyclization reaction of Aryl or 1-alkenyl halides with 1,2-allenyl ketones: scope and mechanism. An efficient assembly of 2,3,4-, 2,3,5-tri- and 2,3,4,5-tetrasubstituted furans

Described herein is the Pd(0)-catalyzed coupling cyclization reaction of 1,2-allenyl ketones with organic halides leading efficiently and conveniently to not only 2,3,4- and 2,3,5-trisubstituted furans but also 2,3,4,5-tetrasubstituted furans. Furthermore, this method showed high substituent-loading capability and tolerance of various substituents. The reactions of 1,2-allenyl ketones 1 e, 1 p, 1 q, and deuterated [D]1 c were performed for a mechanistic study, which demonstrated that instead of an enolization pathway, the reaction may proceed via the intermediacy of dienolate palladium and intramolecular nucleophilic attack on the pi-allyl palladium intermediate by the carbonyl oxygen.