Generation of allyl Grignard reagents via titanocene-catalyzed activation of allyl halides

A protocol for the generation of allyl Grignard reagents via the catalytic activation of allyl halides is described herein. Subsequent nucleophilic addition to carbonyl derivatives provided the desired homo allylic alcohols in excellent yields (84-99%). Evidence suggests that titanocene dichloride catalyzes the formation of an allyl Grignard species which reacts solely with the carbonyl electrophile as evidenced by the complete absence of Würtz coupling. This methodology will have wide-ranging applicability in the generation of highly reactive organometallic reagents.     

烯基Grignard试剂与二苯基卤甲烷的单电子转移反应

作者曾报道,乙烯基溴化镁与二苯基氯甲烷的反应经历单电子转移过程,生成二苯甲基和乙烯基自由基对,导致反应产物四苯乙烷的苄基质子出现CIDNP效应。为了更详细地阐明反应机理,本文报道(Z)-丙烯基溴化镁(1)与二苯基溴甲烷(2)反应的产物,立体化学,并讨论离去基对反应的影响。     

Anionic tricarbonyl derivatives of molybdenum and tungsten and their reactions with allyl halides

A series of carbonylmetallate anions $\text{fac}$-[MX(CO)₃L₂]^?, where M = Mo or W, X = Cl, Br or I and L₂ = 1,10-phenanthroline(phen) or 2,2′-bipyridine(bipy) have been prepared from the corresponding $\text{cis}$-M(CO)₄L₂ complexes. No evidence of $\text{fac}$-to $\text{mer}$-isomerisation was evident on dissolution, although in MeCN solvolysis occurred with the formation of $\text{fac}$-M(CO)₃L₂(MeCN). Reaction of the anions with various allyl halides resulted in high yields of η³-allyl complexes [MX(CO)₂(η³-RC₃H₄)L₂]. The significance of these observations for the mechanism of the allyl oxidative-addition reaction are discussed.     

Photochemical reactions of allyl and crotyl halides with cyclopentadienyl-chromium, -molybdenum and -tungsten complexes

[MoCl(CO)₃(η⁵-C₅H₅)] on photolysis with allyl or crotyl halides C₅H₄RX gives Mo^IV complexes [MoX₂(CO)(η³-C₃H₄R)(η⁵-C₅H₅)] (R = H, X = Cl, Br, I; R = Me, X = Cl, Br). [WCl(CO)₃(η⁵-C₅H₅)] under similar conditions gives trihalides [WX₃(CO)₂(η⁵-C₅H₅)] (X = Cl, Br) on reaction with C₃H₅Cl and C₃H₅Br while [WCl(CO)₃(η⁵-C₅H₄SiMe₃)] and [CrI(CO)₃(η⁵-C₅H₅)] react with allyl chloride to give [WCl₃(CO)₂(η⁵-C₅H₄SiMe₃)] and [CrCl₂(η⁵-C₅H₅)] respectively.     

Nickel-catalyzed monosubstitution of polyfluoroarenes with organozinc reagents using alkoxydiphosphine ligand

A new diphosphine (POP) ligand bearing an alkoxide group allows us to synthesize partially fluorinated arenes. A nickel-catalyzed cross-coupling between a polyfluoroarene and an organozinc reagent in the presence of POP selectively produces a monosubstitution product. Aryl and alkylzinc reagents smoothly take part in the reaction. It is speculated that monosubstitution is the result of accelerated product expulsion from the product/catalyst complex.     

Catalyzed cross-coupling of allyl bromides with allyl tin reagents

The reaction of allyl bromides with allyl tin reagents, catalyzed by palladium or zinc chloride gives cross-coupled products without allylic transpostion in the allyl halide partner but with predominate allylic rearrangement from the tin partner.     

Palladium-catalyzed cross-coupling reactions of in situ generated allylindium reagents with aryl halides

[reaction: see text] In situ generated allylindium reagents from the reaction of 1 equiv of indium with 1.5 equiv of allyl halides could be effective cross-coupling partners in palladium-catalyzed cross-coupling reactions to aryl halides. The best results were obtained with 2% Pd(2)dba(3)CHCl(3) and 16% Ph(3)P in the presence of 3 equiv of LiCl in DMF at 100 degrees C.     

Palladium-catalyzed cross-coupling reactions between dihydropyranylindium reagents and aryl halides. synthesis of C-aryl glycals

[reaction: see text] Palladium(0)-catalyzed cross-coupling reactions between tris(dihydropyranyl)indium 1 and aryl halides 2 have been investigated. Aryl iodides and electron-deficient aryl bromides couple efficiently with the in situ-generated indium reagents in the presence of 1-5 mol % Cl(2)Pd(PPh(3))(2) to produce substituted dihydropyrans 3 with minimal (<10%) dimer (4) formation. Organoindium reagents derived from D-glucal also undergo cross couplings with aryl iodides to produce C-aryl glycals.     

Silver-catalyzed benzylation and allylation reactions of tertiary and secondary alkyl halides with grignard reagents

Treatment of alkyl halides, including tertiary alkyl bromides, with benzylic or allylic Grignard reagent in the presence of a catalytic amount of silver nitrate in ether yielded the corresponding cross-coupling products in high yields. The coupling reactions of tertiary alkyl halides provide efficient access to quaternary carbon centers.     

Amination reactions of aryl halides with nitrogen-containing reagents mediated by palladium/imidazolium salt systems.

Nucleophilic N-heterocyclic carbenes have been conveniently used as catalyst modifiers in amination reactions involving aryl chlorides, aryl bromides, and aryl iodides with various nitrogen-containing substrates. The scope of a coupling process using a Pd(0) or Pd(II) source and an imidazolium salt in the presence of a base, KO(t)Bu or NaOH, was tested using various substrates. The Pd(2)(dba)(3)/IPr.HCl (1, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) system presents the highest activity with respect to electron-neutral and electron-rich aryl chlorides. The ligand is also effective for the synthesis of benzophenone imines, which can be easily converted to the corresponding primary amines by acid hydrolysis. Less reactive indoles were converted to N-aryl-substituted indoles using as supporting ligand the more donating SIPr.HCl (5, SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene). The Pd(OAc)(2)/SIPr.HCl/NaOH system is efficient for the N-arylation of diverse indoles with aryl bromides. The general protocol developed has been applied successfully to the synthesis of a key intermediate in the synthesis of an important new antibiotic. Mechanistically, palladium-to-ligand ratio studies strongly support an active species bearing one nucleophilic carbene ligand.     

Electrophilic reactions of halides of group vi elements. 7. Reactions of allylbenzene and allyl phenyl ether with selenium tetrahalides

The reaction of selenium tetrachloride with allylbenzene and allyl phenyl ether proceeds in accordance with the Markownikoff rule to give 1:2 adducts. The use of selenium tetrabromide changes the course of the reaction and leads to the production of a mixture of adducts in accordance with and counter to the Markownikoff rule, as well as products of cyclization of the intermediate monoadducts to 2-bromomethyl-2,3-dihydrobenzo[b]selenophene or 2-bromomethyl-benzo-1,4-selenoxane derivatives.See [1–6] for previous communications.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 911–913, July, 1982.     

Synthesis of allylamides from allyl halides, carbon monoxide, and titanium-nitrogen complexes prepared from molecular nitrogen

4-Phenylbut-3-enamide could be synthesized from corresponding 3-chloroprop-2-enylbenzene, carbon monoxide (1 atm), and titanium-nitrogen complexes, prepared from Ti(OⁱPr)₄, Li, TMSCl, and molecular nitrogen (1 atm), using a palladium catalyst. The reaction proceeds via transmetalation of the titanium-nitrogen complex to an acylpalladium complex. P^tBu₃ as a ligand of the palladium catalyst, afforded a good result, and the amounts of Li and TMSCl affected the yield of amide. When the reaction was carried out using a bidentate ligand on the palladium complex under an atmosphere of argon instead of carbon monoxide, an allylamine derivative was obtained.     

Synthesis and reactions of substituted nitro-allylating reagents

Nitro-cyclohexenylation and α-phenyl-nitro-allylation of nucleophilic centres are achieved (see $\text{11}$-$\text{16}$) with the nitroallyl pivalates $\text{2}$ and $\text{5}$, and with the chloride $\text{3}$, which are in turn prepared from the diols $\text{9}$ and $\text{10}$, respectively.     

Palladium-catalyzed reaction of allyl halides with alpha-diazocarbonyl compounds

The Pd(OAc)(2)-catalyzed reaction between alpha-diazocarbonyl compounds and allyl bromides or chlorides leads to the formation of 1,3-diene derivatives.     

Stereochemistry of the nickel-catalyzed cross-coupling reaction of Grignard reagents with olefinic halides: stereospecific versus nonstereospecific-stereoselective reactions

The nickel-catalyzed cross-coupling reactions of Grignard reagents with monohalo-olefins proceed stereospecifically, while with 1,2-dihaloethylenes they proceed nonstereo-specifically to form cis-olefins stereoselectively in many cases.