Showing papers on "Heck reaction published in 1992"

Generation of Tertiary Phosphine-Coordinated Pd(0) Species from Pd(OAc)2 in the Catalytic Heck Reaction

Abstract: Palladium(II) diacetate reacted with water (1 equiv./Pd) and (R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl ((R)-BINAP) (3 equiv./Pd) in benzene in the presence of Et3N to give the palladium(0) species Pd[(R)-BINAP]2 (1 equiv./Pd), (R)-BINAP monoxide (1 equiv./Pd), and Et3N·HOAc (2 equiv./Pd). The progress of reaction strongly affected by the content of water in the reaction solution. The reduction of Pd(OAc)2 in the presence of PPh3 proceeded in a similar process to give Pd(PPh3)4 and OPPh3.

A Palladium-Mediated Approach to Construction of Nitrogen Heterocycles

Abstract: Sequential regiospecific C-C and C-N bond-forming reactions via a novel variation of the Heck reaction can be used to synthesize nitrogen-containing heterocyclic systems

Palladium-catalysed polycyclization of dienynes to give carbocyclic angularly bisanellated cyclohexadlene derivatives

Abstract: Various 2-bromododeca-1,11-dien-6-ynes 1a,b,8 and trans- or cis-10a,b when subjected to Heck reaction conditions, cleanly undergo palladium-catalysed biscyclizations followed by an electrocyclic rearrangement to form tricyclic cyclohexadienes 5a,b, 9 and cis- or trans-11a,b as sole products (7 examples).

Mesomorphic Metal Complexes Derived from 4-Alkyl-oxystilbazoles

Abstract: The weakly mesomorphic trans-4-alkyloxy-4′-stilbazoles(n-OPhVPy) are readily synthesised from alkyloxyiodobenzenes and 4-vinylpyridine in a palladium-catalysed Heck reaction. While the highly symmetric palladium and platinum complexes trans-[MCl2(n-OPhVPy)2] show mesophases only at very high temperatures, the lower symmetry platinum complexes trans-[PtCl2(η2-olefin) (n-OPhVPy)] melt below 100°C. Similarly, the complexes [MCl(CO)2(n-OPhVPy)] (M = Rh, Ir) are low melting. The silver complexes [Ag(n-OPhVPy)2][X] (X = C12H25OSO3, C8H17OSO3, CF3SO3) can be obtained by direct reaction of the stilbazole with AgX. These ionic materials show a rich thermotropic polymorphism, including nematic and cubic mesophases. Some fluorinated stilbazoles have also been synthesised and complexed to silver; the mesomorphism of these complexes is also reported.

Novel and efficient synthesis of rotenoids via intramolecular radical arylation

Abstract: Treatment of the iodoarylchromenes 22 with palladium acetate gave the tetracyclic compounds 23via a formal but stereochemically disallowed Heck reaction; a crystalline intermediate palladium species 25(X-ray analysis) was isolated. The method was employed to synthesise the natural rotenoid (±)-munduserone 29. Related reductive radical cyclisation of enol acetate 31 gave the (±)-6aα,12a,12aα-chromenochromenol acetate 32(R = Ac), representing the core structure of the insecticidal rotenoid 2, in a 5 step (15% overall) route from 2-methylthiomethylchromone 17. The cis,cis-geometry is obtained stereospecifically through an intramolecular 6-exo addition mode.

Domino-Heck Coupling of Aryl Halides and Dicyclopentadiene: A Simple Access to Polycyclic Arene-Anellated Cyclopentadienes as Ligands for Metal Complexes

Abstract: Domino coupling products of haloarenes and norbornene as well as dicyclopentadiene can be converted to polycyclic aromatic compounds like benzo[e]pyrene (3), benzo[e]cyclopenta[I]pyrene (4), 7-phenyl-1H-cyclopenta[I]phenanthrene (10) and 1H-cyclopenta[f][3,8]phenanthroline (16). Compounds 4 and 10 can serve as new ligands in metal complexes such as ferrocenes 17, 18a and titanocene 18b.

Catalytic Asymmetric Synthesis of Polycylic Compounds by Asymmetric Heck Reaction

Abstract: In 1989, we succeeded in demonstrating the first example of an asymmetric Heck reaction. Treatment of the prochiral alkenyl iodide 4 b with Cl2Pd (R) -BINAP (10 mol%), Ag3PO4 (2 molar equiv) and CaCO3 (2.2 molar equiv) in 1-methyl-2-pyrrolidinone produced the cis-decalin derivative 8 b with 80% ee. The result suggested that the presence of a silver salt produced the Pd+ intermediate 11 with 16-electron configuration by abstraction of I- to result in the formation of 8 b with high ee. Under the similar conditions, the cis-decalin derivative 18 of 92% ee and the cis-hydrindan derivative 26 a of 86% ee were obtained from the corresponding alkenyl iodides, respectively, On the other hand, it was found that treatment of the prochiral alkenyl triflate 19 d with Pd (OAc) 2 (5 mol%), (R) -BINAP (10 mol%) and K2CO3 (2 molar equiv) in toluene gave 8 d in 91% ee. Furthermore, 27 was cyclized to 26 b in 73% ee under the similar conditions, which was successfully transformed into the key intermediate 34 for oppositol. An asymmetric Heck reaction was also useful for the synthesis of polycyclopentanoids. Thus, the prochiral alkenyl triflate 59 was treated with 1.7 mol% of Pd (0Ac) 2, 2.1 mol% of (S) -BINAP and 1.7 equiv of tetrabutylammonium acetate in DMSO afforded the cyclopentanoid 60 of 80% ee in 89% yield. The reaction was found to be useful as well for the capture by a C-centered nucleophile instead of tetrabutylammonium acetate, giving 68 c of 80% ee in one-step from 59. The cyclopentanoid 60 was converted to 43 in a seven-step process, which is a key synthetic intermediate for capnellenols.

A Catalytic Asymmetric Synthesis of Hydrindans.

Abstract: The cis -hydrindan derivative 14b has been synthesized in up to 86% ee by an asymmetric Heck reaction starting with the prochiral alkenyl iodide 9b or the alkenyl triflate 13 .

Intramolecular Heck Reaction with Substrates Possessing an Allylic Alcohol Moiety.

Abstract: In this paper we report our investigation on a series of palladium catalysed cyclisations with substrates possessing an allylic alcohol moiety. This methodology provides a good approach to a wide variety of functionalised 5 or 6 membered carbo- or heterocycles. We also demonstrate that it is possible to combine an alkylation and a cyclisation process using the same palladium catalyst system.

Further Studies on a Catalytic Asymmetric Synthesis of Decalin Derivatives.

Abstract: The decalin derivatives 2 (92% ee) and 18c (92% ee) were synthesized from the corresponding prochiral substrates 7b and 17a by an asymmetric Heck reaction.

A General Solution to the Synthesis of 2-Azabicyclo(3.3.1)nonane Unit of Strychnos Alkaloids.

Abstract: The characteristic 2-azabicyclo[3.3.1]nonane substructure of Strychnos alkaloids can be constructed rapidly and stereospecifically using an intramolecular Heck reaction.