Pd(OH)2/C (Pearlman's catalyst): a highly active catalyst for Fukuyama,Sonogashira, and Suzuki coupling reactions

Treatment of thiol esters 1 with zinc reagent 2 in the presence of a small amount (相似文献   

An acid-catalyzed macrolactonization protocol

[reaction: see text] An efficient macrolactonization protocol devoid of any base was developed derived from the use of vinyl esters in transesterification. Subjecting a hydroxy acid and ethoxyacetylene to 2 mol % [RuCl(2)(p-cymene)](2) in toluene followed by addition of camphorsulfonic acid or inverse addition provided macrolactones in good yields.     

Palladium-catalyzed α-regioselective allylic amination of Morita-Baylis-Hillman acetates with simple aromatic amines

An efficient allylic amination of Morita-Baylis-Hillman acetates with simple aromatic amines provided good yields with excellent α-regioselectivity (up to exclusive α-product) under the catalysis of Pd(2)(dba)(3)/ferrocene-type diphosphine ligand.     

Allylation of alcohols and carboxylic acids with allyl acetate catalyzed by [Ir(cod)2](+)BF4- complex

A facile method for the synthesis of allyl alkyl ethers from alcohols with allyl acetate was developed by the use of [Ir(cod)(2)](+)BF(4)(-) complex. For instance, the reaction of allyl acetate with n-octyl alcohol in the presence of a catalytic amount of [Ir(cod)(2)](+)BF(4)(-) complex afforded allyl octyl ether in quantitative yield. Allyl carboxylates were also prepared by the exchange reaction between carboxylic acids and allyl acetate in good yields. The [Ir(cod)(2)](+)BF(4)(-) complex catalyzed the reaction of alkyl and aromatic amines with allyl acetate to lead to the corresponding allylamines in fair to good yields.     

Catalytic and enantioselective aza-ene and hetero-Diels-Alder reactions of alkenes and dienes with azodicarboxylates

Lewis acids such as Cu(OTf)(2), Zn(OTf)(2), Yb(OTf)(3) and Nd(OTf)(3) catalyze the aza-ene reaction of alkenes with azodicarboxylates, giving the allylic amination adducts. The use of bis(2,2,2-trichloroethyl)azodicarboxylate as the amination reagent and Cu(OTf)(2) and Yb(OTf)(3) as the catalysts gave the aza-ene reaction of different alkenes, leading to the corresponding allyl amines in high yields. Chiral copper complexes prepared from Cu(OTf)(2) and chiral bisoxazoline ligands were found to catalyze the enantioselective aza-ene reaction of azodicarboxylates with alkenes and the hetero-Diels-Alder reaction with cyclopentadiene, giving the corresponding aza-ene- and hetero-Diels-Alder adducts, respectively, in good yields and moderate enantioselectivities.     

Palladium-catalyzed borylation of phenyl bromides and application in one-pot Suzuki-Miyaura biphenyl synthesis

The coupling reaction of pinacolborane with various aryl bromides in the presence of a catalytic amount of Pd(OAc)(2) together with DPEphos as ligand and Et(3)N as base provided arylboronates. High yields were obtained in the case of electron-donor substituted aryl bromides. The direct preparation of arylboronates allowed the one-pot, two-step synthesis of unsymmetrical biaryls in high yields. [reaction: see text]     

The first alpha-fluoroallenylphosphonate, the synthesis of conjugated fluoroenynes, and the stereoselective synthesis of vinylfluorophosphonates using a new multifunctional fluorine-containing building block

Limitations on current methodologies for the introduction of CF(2) and CFH in complex alpha-fluorophosphonates led to the synthesis of a fluorine-containing building block TIPS-C&tbd1;CCFXP(O)(OEt)(2), where X = H or F. This multifunctional fluorine synthon reacts with carbonyl compounds under WHE conditions to give high yields of fluorinated conjugated enynes and enediyne. When X = F, trapping of the desilylated anion with an electrophile after TIPS removal provided exclusive access to gamma-substituted derivatives of alpha-fluorophosphonates. When X = H, TBAF deprotection of the silyl group yields H(2)C=C=CFP(O)(OEt)(2) through an allenyl-propargyl resonance stabilized anion. The allene moiety has been used as template in the stereoselective synthesis of alpha-fluoro-beta, gamma-diiodopropenyl phosphonate, via electrophilic iodination, and alpha-fluoro-gamma-amino-alpha,beta-unsaturated phosphonates, including unsaturated phosphononucleosides, by nucleophilic displacement of an allylic iodide. Hydroamination of H(2)C=C=CFP(O)(OEt)(2) using secondary amines produced (Z)-alpha-fluoroenaminophosphonates, whereas Diels-Alder cycloaddition with cyclopentadiene provides the corresponding exocyclic vinylfluorophosphonate.     

Recent applications of the (TMS)3SiH radical-based reagent

This review article focuses on the recent applications of tris(trimethylsilyl)silane as a radical-based reagent in organic chemistry. Numerous examples of the successful use of (TMS)(3)SiH in radical reductions, hydrosilylation and consecutive radical reactions are given. The use of (TMS)(3)SiH allows reactions to be carried out under mild conditions with excellent yields of products and remarkable chemo-, regio-, and stereoselectivity. The strategic role of (TMS)(3)SiH in polymerization is underlined with emphasis on the photo-induced radical polymerization of olefins and photo-promoted cationic polymerization of epoxides.     

Switch in stereoselectivity caused by the isocyanide structure in the rhodium-catalyzed silylimination of alkynes

The reaction of terminal alkynes with hydrosilanes and tert-alkyl isocyanides in the presence of Rh(4)(CO)(12) gives (Z)-β-silyl-α,β-unsaturated imines in good yields. On the other hand, the use of aryl isocyanides in place of tert-alkyl isocyanides leads to the formation of E isomers.     

Ruthenium-Lewis acid catalyzed asymmetric Diels-Alder reactions between dienes and alpha,beta-unsaturated ketones

The complex [Ru(Cp)(R,R-BIPHOP-F)(acetone)][SbF(6)], (R,R)-1 a, was used as catalyst for asymmetric Diels-Alder reactions between dienes (cyclopentadiene, methylcyclopentadiene, isoprene, 2,3-dimethylbutadiene) and alpha,beta-unsaturated ketones (methyl vinyl ketone (MVK), ethyl vinyl ketone, divinyl ketone, alpha-bromovinyl methyl ketone and alpha-chlorovinyl methyl ketone). The cycloaddition products were obtained in yields of 50-90 % and with enantioselectivities up to 96 % ee. Ethyl vinyl ketone, divinyl ketone and the halogenated vinyl ketones worked best and their reactions with acyclic dienes consistently provided products with >90 % ee. alpha-Chlorovinyl methyl ketone performed better than alpha-bromovinyl methyl ketone. The reaction also provided a [4.3.1]bicyclic ring system in 95 % ee through an intramolecular cycloaddition reaction. Crystal structure determinations of [Ru(Cp)((S,S)-BIPHOP-F)(mvk)][SbF(6)], (S,S)-1 b, and [Ru(Cp)((R,R)-Me(4)BIPHOP-F)(acrolein)][SbF(6)], (R,R)-2 b, provided the basis for a rationalization of the asymmetric induction.     

A remarkably efficient coupling of acid chlorides with alkynes in water

[reaction: see text] A highly effective direct coupling of acid chloride with terminal alkynes catalyzed by PdCl(2)(PPh(3))(2)/CuI together with a catalytic amount of sodium lauryl sulfate as the surfactant and K(2)CO(3) as the base provided ynones in high yields in water.     

Indol-2-ylidene (IdY): Ambiphilic N-Heterocyclic Carbene Derived from Indole**

The synthesis of ambiphilic N-heterocyclic carbene ligand, indol-2-ylidene (IdY, A ), is described. A series of indolenium precursors ( 2 a – f ) were prepared on a gram scale in good yields. Trapping experiments with elemental selenium, [RhCl(cod)]₂ and CuCl provided the expected carbene adducts. Further computational and spectroscopic studies supported the ambiphilicity of IdY, which lies between cyclic (alkyl)(amino)carbenes (CAAC-5) and cyclic (amino)(aryl)carbene (CAArC). The copper complexes ( 6 ) show high percent buried volume (% V_bur = 58.1) and allow for carboboration of terminal alkynes within 30 minutes in a demonstration of synthetic utility with good yields and high regioselectivity.     

Solid state coordination chemistry: construction of 2D networks and 3D frameworks from phosphomolybdate clusters and binuclear Cu(II) complexes. The syntheses and structures of [(Cu2(tpypyz)(H2O)2)(Mo5O15)(HOPO3)2].nH2O [n = 2, 3; tpypyz = tetra(2-pyridyl)pyrazine

The hydrothermal reaction of MoO3, Cu(C2H3O2)2.H2O, tpypyz, H3PO4 and H2O yields a 2D material, [(Cu2(tpypyz)(H2O)2)(Mo5O15)(HOPO3)2].2H2O (1.2H2O), constructed from (Mo5O15(HOPO3)2)4- clusters linked through (Cu2(tpypyz)(H2O)2)2+ components; in contrast, use of Cu2O in the synthesis in place of Cu(C2H3O2)2.H2O yields a 3D material [(Cu2(tpypyz)(H2O)2)(Mo5O15)(HOPO3)2].3H2O (2.3H2O), constructed from the same building blocks as 1.2H2O.     

Room temperature asymmetric allylic trifluoromethylation of Morita-Baylis-Hillman carbonates

(DHQD)(2)PHAL-catalyzed asymmetric allylic trifluoromethylation of Morita-Baylis-Hillman adducts using a Rupert-Prakash reagent is reported. This transformation provided the S(N)2' trifluoromethylated products with good yields and excellent enantioselectivities at room temperature. It was also found that the reaction could be accelerated using acetonitrile as cosolvent.     

Silver-catalyzed intramolecular aminofluorination of activated allenes

A nice combination: The intramolecular oxidative aminofluorination of allenes using silver catalysis and FN(SO(2) Ph)(2) as the fluorinating reagent has been developed. This reaction represents an efficient method for the synthesis of various 4-fluoro-2,5-dihydropyrrole compounds. Further transformation provided the corresponding fluorinated pyrrole derivatives in good yields.     

Novel photoacid generators for photodirected oligonucleotide synthesis

Photodirected oligonucleotide synthesis uses either direct or indirect light-dependent 5'-deprotection. Both have been reported to give lower stepwise synthetic yields than conventional methods. The deficiency appears to be due to incomplete deprotection at the oligonucleotide 5'-position and, additionally in the case where photodirection is indirect and uses photogenerated photoacid to effect 5'-detritylation, the depurinating effects of strong acid. We have developed novel photosensitive-2-nitrobenzyl esters that on irradiation with near UV light generate alpha-chloro-substituted acetic acids, such as trichloroacetic acid, which are widely and successfully used in conventional solid-phase oligonucleotide synthesis. alpha-Phenyl-4,5-dimethoxy-2-nitrobenzyltrichloroacetate and alpha-phenyl-4,5-dimethoxy-2,6-dinitrobenzyltrichloroacetate showed appropriate photochemical characteristics and were used for photodirected synthesis of a variety of oligonucleotides, including (T)(5), TATAT, TGTGT, (T)(10), (AT)(5), (CT)(5) (GT)(5), and (TGCAT)(2) on a modified Millipore Expedite DNA synthesizer. The outcomes were compared with those obtained by use of directly added trichloroacetic acid (conventional synthesis). The stepwise yields for the two methods were essentially identical.     

A mild Negishi cross-coupling of 2-heterocyclic organozinc reagents and aryl chlorides

A mild Negishi cross-coupling of 2-heterocyclic organozinc reagents and aryl chlorides is described. The use of Pd(2)(dba)(3) and X-Phos as a ligand provides high yields for many examples. An efficient method to generate the organozinc reagents at room temperature is also demonstrated.     

A facile regiocontrol in the palladium-catalyzed annulation of fluorine-containing internal alkynes with variously substituted 2-iodoanilines: a new regioselective synthesis of 2- or 3-fluoroalkylated indole derivatives

Treatment of various types of fluoroalkylated alkynes with o-iodoaniline in the presence of Pd(PPh(3))(4) in DMF at 80 degrees C for 8 h mainly gave 2-fluoroalkylated indoles in high yields. The use of P(o-Tol)(3) instead of PPh(3) as a ligand led to the preferential formation of 3-fluoroalkylated indoles in high yields. Interestingly, the reaction of trifluoromethylated alkynes bearing a benzylic substituent afforded 2- or 3-trifluoroethylated indole derivatives in good yields.     

Effects of large halides on the structures of lanthanide(III) and plutonium(III) borates

Reactions of LnBr(3) or LnOI with molten boric acid result in formation of Ln[B(5)O(8)(OH)(H(2)O)(2)Br] (Ln = La-Pr), Nd(4)[B(18)O(25)(OH)(13)Br(3)], or Ln[B(5)O(8)(OH)(H(2)O)(2)I] (Ln = La-Nd). Reaction of PuOI with molten boric acid yields Pu[B(7)O(11)(OH)(H(2)O)(2)I]. The Ln(III) and Pu(III) centers in these compounds are found as nine-coordinate hula-hoop or 10-coordinate capped triangular cupola geometries where there are six approximately coplanar oxygen donors provided by triangular holes in the polyborate sheets. The borate sheets are connected into three-dimensional networks by additional BO(3) triangles and/or BO(4) tetrahedra that are roughly perpendicular to the layers. The room-temperature absorption spectrum of single crystals of Pu[B(7)O(11)(OH)(H(2)O)(2)I] shows characteristic f-f transitions for Pu(III) that are essentially indistinguishable from Pu(III) in other compounds with alternative ligands and different coordination environments.     

Enantioselective synthesis of β-pyrazole-substituted alcohols through an asymmetric ring-opening reaction of meso-epoxides

An efficient and practical synthesis of optically pure β-pyrazole-substituted alcohols was achieved by an asymmetric ring-opening reaction of meso-epoxides with pyrazole derivatives as the nucleophile. In the presence of 1?mol?% of an N,N'-dioxide-Sc(OTf)(3) complex, excellent enantioselectivity and yields were obtained from meso-epoxides. The process could also be used for a mixture of cis- and trans-stilbene oxides. A proposed transition-state model is provided.