二茂铁咪唑盐的合成及其在Suzuki-Miyaura反应中的应用

合成了硫醚官能化、膦官能化及未官能化的二茂铁咪唑盐,并研究了以其作为N-杂环卡宾配体前体对Pd催化的Suzuki-Miyaura偶联反应的影响,发现在4-甲基溴苯与苯硼酸偶联反应中以膦官能化的配体对催化性能提高有利,而硫醚官能化不利于催化性能提高。     

Synthetic Utilization of α-Phosphonovinyl Anions

The α-phosphonovinyl anions, generated in situ from treatment of β-hetero-substituted vinyl-phosphonates 1a-c with LDA (or LTMP), were trapped with various electrophiles such as chlorotriorganosilanes, chlorotrimethylgermane, chlorotriorganotins, dimethyl disulfide, and halogen to afford the corresponding β-hetero-substituted α-functionalized vinylphosphonates 2–14 in good to excellent yields. The Friedel-Crafts reaction of α-(silyl) or α-(germyl)phosphonoketene dithioacetals 2, 9 or 4 with acid chlorides gave α-acylated phosphonoketene dithioacetals 15–19 in 53–91 % yields. The palladium-catalyzed cross-coupling reaction of β-ethoxy-α-(tributylstannyl)vinylphosphonate 13 with a variety of organic halides (R = acyl, allyl, aryl etc.) provided β-ethoxy-α-substituted vinylphosphonates 20–25 in good to moderate yields. The palladium-mediated cross-coupling reaction of α-(iodo)-vinyl-phosphonates 7, 14 with terminal acetylenes afforded α-alkynylated vinylphosphonates 26–29 in 69–83 % yields.     

Stereoselective sp-sp bond formation via Negishi cross-coupling of vinylic tellurides and 2-heteroarylzinc chlorides

The Negishi cross-coupling reaction of vinylic- and aryltellurides with heteroarylzinc chlorides catalyzed by PdCl₂/CuI is described. This cross-coupling reaction is general and permits the formation of a new sp²-sp² carbon bond in good yields and high stereoselectivity.     

Microwave-promoted Suzuki-Miyaura coupling reactions in a cycloalkane-based thermomorphic biphasic system

Microwave-promoted Suzuki-Miyaura coupling reaction of aryl halides attached to a cycloalkane-soluble platform was accomplished in a cycloalkane-based thermomorphic biphasic system. Following irradiation and subsequent cooling, the monophasic reaction mixture immediately formed a biphasic solution to allow facile workup and separation of the product.     

Cobalt‐Catalyzed Cross‐Coupling of Functionalized Alkylzinc Reagents with (Hetero)Aryl Halides

A combination of 10 % CoCl₂ and 20 % 2,2′‐bipyridine ligands enables cross‐coupling of functionalized primary and secondary alkylzinc reagents with various (hetero)aryl halides. Couplings with 1,3‐ and 1,4‐substituted cycloalkylzinc reagents proceeded diastereoselectively leading to functionalized heterocycles with high diastereoselectivities of up to 98:2. Furthermore, alkynyl bromides react with primary and secondary alkylzinc reagents providing the alkylated alkynes.     

Mechanistic Dichotomy of Magnesium‐ and Zinc‐Based Germanium Nucleophiles in the C(sp3)−Ge Cross‐Coupling with Alkyl Electrophiles

Robust procedures for two mechanistically distinct C(sp³)?Ge bond formations from alkyl electrophiles and germanium nucleophiles are reported. The germanium reagents were made available as bench‐stable solutions by lithium‐to‐magnesium and lithium‐to‐zinc transmetalation, respectively. The germanium Grignard reagent reacts with various primary and secondary alkyl electrophiles by an ionic nucleophilic displacement. Conversely, the coupling of the corresponding zinc reagent requires a nickel catalyst, which then engages in radical bond formations with primary, secondary, and even tertiary alkyl bromides. Both methods avoid the regioselectivity issue of alkene hydrogermylation and enable the synthesis of a wide range of functionalized alkyl‐substituted germanes.     

Bis(triphenylphosphine)palladium(II)succinimide as a precatalyst for Suzuki cross-coupling—subtle effects exerted by the succinimide ligand

A new palladium(II) precatalyst for Suzuki cross-coupling of aryl halides and organoboronic acids has been identified, namely bis(triphenylphosphine)palladium(II)succinimide [(Ph₃P)₂Pd(N-Succ)₂] 2. The precatalyst is easily prepared from palladium(0) precursors, such as (Ph₃P)₄Pd or Pd₂dba₃·CHCl₃/Ph₃P and succinimide, is air, light and moisture stable, and may be employed with a variety of substrates to give the cross-coupled products, in good yields and in reasonable time, at relatively low catalyst loadings.     

Efficient preparation of (Z)-alkenyl derivatives from (Z)-vinyl (N,N-diisopropyl)carbamate via Ni-catalysed coupling reactions

A (Z)-vinyl (N,N-diisopropyl)carbamate treated with Grignard reagents, under Wenkert Nickel-catalysed conditions, gave access to several substituted (Z)-alkenyl derivatives. These Nickel-catalysed reactions, carried out with vinyl-, phenyl-, p-methoxyphenyl-, trimethylsilylmethylmagnesium bromide and benzylmagnesium chloride, led to the corresponding (Z)-alkenyl derivatives in good yields and high stereoselectivities.     

Phosphine free diamino-diol based palladium catalysts and their application in Suzuki-Miyaura cross-coupling reactions

Inexpensive air and moisture stable diamino-diol ligands [(2-OH-C₁₀H₆)CH₂(μ-NC₄H₈N)CH₂(C₁₀H₆-2-OH)] (1) and [(5-^tBuC₆H₃-2-OH)CH₂(μ-NC₄H₈N)CH₂(5-^tBuC₆H₃-2-OH)] (2) were synthesized by reacting corresponding alcohols with formaldehyde and piperazine. Treatment of ligands 1 and 2 with Pd(OAc)₂ in 1:1 molar ratio afforded neutral palladium complexes [Pd{(OC₁₀H₆)CH₂(μ-NC₄H₈N)CH₂(C₁₀H₆O)}] (3) and [Pd{(5-^tBuC₆H₃-2-O)CH₂(μ-NC₄H₈N)CH₂(5-^tBuC₆H₃-2-O)}] (4) in good yield. The palladium complexes 3 and 4 are employed in Suzuki-Miyaura cross-coupling reactions between phenylboronic acid and several aryl chlorides or bromides. They are found to be competent homogeneous catalysts for a variety of substrates to afford the coupled products in good to excellent yields. The crystal structures of compounds 2 and 4 are also reported.     

NIR‐Absorbing Donor–Acceptor Based 1,1,4,4‐Tetracyanobuta‐1,3‐Diene (TCBD)‐ and Cyclohexa‐2,5‐Diene‐1,4‐Ylidene‐Expanded TCBD‐Substituted Ferrocenyl Phenothiazines

A series of unsymmetrical (D‐A‐D₁, D₁‐π‐D‐A‐D₁, and D₁‐A₁‐D‐A₂‐D₁; A=acceptor, D=donor) and symmetrical (D₁‐A‐D‐A‐D₁) phenothiazines ( 4 b , 4 c , 4 c′ , 5 b , 5 c , 5 d , 5 d′ , 5 e , 5 e′ , 5 f , and 5 f′ ) were designed and synthesized by a [2+2] cycloaddition–electrocyclic ring‐opening reaction of ferrocenyl‐substituted phenothiazines with tetracyanoethylene (TCNE) and 7,7,8,8‐tetracyanoquinodimethane (TCNQ). The photophysical, electrochemical, and computational studies show a strong charge‐transfer (CT) interaction in the phenothiazine derivatives that can be tuned by varying the number of TCNE/TCNQ acceptors. Phenothiazines 4 b , 4 c , 4 c′ , 5 b , 5 c , 5 d , 5 d′ , 5 e , 5 e′ , 5 f and 5 f′ show redshifted absorption in the λ =400 to 900 nm region, as a result of a low HOMO–LUMO gap, which is supported by TD‐DFT calculations. The electrochemical study exhibits reduction waves at low potential due to strong 1,1,4,4‐tetracyanobuta‐1,3‐diene (TCBD) and cyclohexa‐2,5‐diene‐1,4‐ylidene‐expanded TCBD acceptors. The incorporation of cyclohexa‐2,5‐diene‐1,4‐ylidene‐expanded TCBD stabilized the LUMO energy level to a greater extent than TCBD.