complexes as useful catalysts in the addition and/or insertion reaction of ethyl diazoacetate to ... more complexes as useful catalysts in the addition and/or insertion reaction of ethyl diazoacetate to saturated or unsaturated substrates; 31 refs.]. -(DIAZ-REQUEJO, M. M.; PEREZ, P. J.; J. Organomet. Chem. 690 (2005) 24-25, 5441-5450; Lab. Catal. Homogenea, Dep. Quim. Cienc. Mater., Univ. Huelva, E-21007 Huelva, Spain; Eng.) -Klein 25-233
The selectivity of the cyclopropanation of olefins with ethyl phenyldiazoacetate has been tested ... more The selectivity of the cyclopropanation of olefins with ethyl phenyldiazoacetate has been tested using different gold complexes bearing phosphine, phosphite or N-heterocyclic as ligands. A comparative study with related copper and silver complexes as catalysts is also presented.
Even in the context of hydrocarbons&a... more Even in the context of hydrocarbons' general resistance to selective functionalization, methane's volatility and strong bonds pose a particular challenge. We report here that silver complexes bearing perfluorinated indazolylborate ligands catalyze the reaction of methane (CH(4)) with ethyl diazoacetate (N(2)CHCO(2)Et) to yield ethyl propionate (CH(3)CH(2)CO(2)Et). The use of supercritical carbon dioxide (scCO(2)) as the solvent is key to the reaction's success. Although the catalyst is only sparingly soluble in CH(4)/CO(2) mixtures, optimized conditions presently result in a 19% yield of ethyl propionate (based on starting quantity of the diazoester) at 40°C over 14 hours.
ABSTRACT A series of complexes Tp(x)Cu (Tp(x) = homoscorpionate ligand) have been tested as the c... more ABSTRACT A series of complexes Tp(x)Cu (Tp(x) = homoscorpionate ligand) have been tested as the catalysts for the olefin aziridination reaction using PhINTs as the nitrene source. Very high yields of aziridines have been obtained with a group of representative substrates, including nonactivated terminal olefins. The high activity of these catalysts has allowed the use of equimolar amounts of PhINTs and olefins, avoiding the requirement of excess olefin. In an effort to eliminate nondesired byproducts, chloramine-T has been employed as the nitrene source, in a reaction that produces sodium chloride as the sole residue, with high degrees of conversions also being obtained.
Kinetic studies of the ethyl diazoacetate (EDA) decomposition reaction in the presence of BpCu (1... more Kinetic studies of the ethyl diazoacetate (EDA) decomposition reaction in the presence of BpCu (1) and in the presence or absence of olefin have led to the determination of several kinetic and thermodynamic parameters, and a consistent mechanism has been proposed for the olefin cyclopropanation reaction. Related studies with the complexes [Cu(bipy) 2 ]I (bipy ) bipyridine) and [Cu(bis(oxazoline)) 2 ]OTf have shown strong similarities with the results obtained with 1. A general mechanism covering the copper-based systems reported in the literature has been proposed, the real catalyst (i.e., the species to be reacted with EDA) in all cases being a neutral, 14-electron fragment of composition (L-L)Cu (L-L ) Bp-and Tp-like ligands, semicorrins, salicylaldehyde derivatives) or, alternatively, the isoelectronic, cationic [(L-L)Cu] + (for L-L ) bis(oxazoline), bipyridine). (22) kobsd values were calculated by means of kobsd ) (1/t) ln([EDA]0/ [EDA]). 17
Carbon-halogen (C-X) bonds (X=Cl, Br) can be easily functionalized with ethyl diazoacetate (N 2 C... more Carbon-halogen (C-X) bonds (X=Cl, Br) can be easily functionalized with ethyl diazoacetate (N 2 CHCO 2 Et) in the presence of silver-based catalysts containing the Tp x Ag core (Tp x = hydrotrispyrazolylborate ligand). Polyhalomethanes are converted into products derived from the formal insertion of the carbene CHCO 2 Et units into the C-X bond. In the case of monohaloalkanes (C 4 -C 6 ), cleavage of the C-X bond is observed, with formation of XCH 2 CO 2 Et and the corresponding olefin. Experimental evidence and theoretical calculations have led to the proposal of a novel mechanism to account for these transformations, in which the metal participates along the pathway in all the reaction steps. Among the experimental data, the first example of a metal-induced, asymmetric functionalization of a C-Cl bond by carbene insertion is included (ee=14 ( 2%). (36) Drudis-Sole, G.; Maseras, F.; Lledos, A.; Vallribera, A.; Moreno-Manas, M. Eur. J. Org. Chem. 2008, 5614.
Copper complexes containing chiral N-heterocyclic carbene ligands catalyze the regioselectiVe nuc... more Copper complexes containing chiral N-heterocyclic carbene ligands catalyze the regioselectiVe nucleophilic boryl attack at the -carbon of R, -unsaturated esters with enantioselectiVities up to 74% ee, depending on the nature of the ester group.
The complexes [Tp Br3 Ag] 2 ‚CH 3 COCH 3 (1) and Tp Br3 Ag(thf) (2) catalyze the insertion of the... more The complexes [Tp Br3 Ag] 2 ‚CH 3 COCH 3 (1) and Tp Br3 Ag(thf) (2) catalyze the insertion of the :CHCO 2 Et group from ethyl diazoacetate (EDA) into the saturated C-H bonds of several C5, C6, and C8 linear and branched alkanes. In addition to secondary and/or tertiary sites, the unprecedented insertion into the primary C-H bonds of the substrates studied has been observed with variable regioselectivity, toward the methyl groups, within the range of 40-60% for branched and nearly 25% for linear alkanes.
Facile alkane functionalization by means of the insertion of :CHCO 2 Et, from ethyl diazoacetate,... more Facile alkane functionalization by means of the insertion of :CHCO 2 Et, from ethyl diazoacetate, into carbon-hydrogen bonds mediated by catalytic amounts of (NHC)MCl (NHC ) N-heterocyclic ligand; M ) Cu, Au) and a halide scavenger MX has been achieved. This chemistry includes the insertion of the carbene fragment into alkane primary positions with Cu-and Au-based catalysts. The nature of the counterion X and of the NHC ligand have a significant effect on the overall yields and regioselectivity of the reaction.
Since its discovery in the late 1970s, Rh 2 (OAc) 4 has been the catalyst of choice for the above... more Since its discovery in the late 1970s, Rh 2 (OAc) 4 has been the catalyst of choice for the above transformations. 5 This complex catalyzes the insertion of several diazo compounds 6,7 into the O−H bond of saturated alcohols at room temperature and in high yield. Other metals ...
The reaction of benzene and ethyl diazoacetate under thermal or photochemical conditions was repo... more The reaction of benzene and ethyl diazoacetate under thermal or photochemical conditions was reported by Büchner almost a century ago. 1 The mixture of cycloheptatrienes obtained in that way was formed upon the formal addition of a carbene group to a double bond of ...
DFT Becke3LYP calculations are applied to the computational study of the activation of alkane C−H... more DFT Becke3LYP calculations are applied to the computational study of the activation of alkane C−H bonds by metallocarbene homoscorpionate complexes. A total of 16 different combinations of metallocarbene complex and alkane are explored, defined by the use of TpAg C(H)(CO ...
Complexes of general formula Tp x Cu (Tp x = homoscorpionate ligand) have been employed as cataly... more Complexes of general formula Tp x Cu (Tp x = homoscorpionate ligand) have been employed as catalysts for the insertion of ethyl diazoacetate into C−H bonds of a variety of hydrocarbons and ethers, in moderate to high yields: tertiary, secondary, and primary C−H bonds have ...
The complex {[HC(3,5-Me 2 pz) 3 ]Cu(NCMe)}BF 4 catalyzes the transfer of the :CHCO 2 Et unit from... more The complex {[HC(3,5-Me 2 pz) 3 ]Cu(NCMe)}BF 4 catalyzes the transfer of the :CHCO 2 Et unit from ethyl diazoacetate to several saturated and unsaturated substrates with very high yields and under biphasic conditions using the ionic liquid [bmim][PF 6 ] and hexane as the reaction medium. The catalyst has been tested for several cycles of recovery and reuse without any loss of activity.
Page 1. Controlled, Copper-Catalyzed Functionalization of Polyolefins M. Mar Dı´az-Requejo,† Pete... more Page 1. Controlled, Copper-Catalyzed Functionalization of Polyolefins M. Mar Dı´az-Requejo,† Peter Wehrmann,‡ Mark D. Leatherman,§ Swiatoslaw Trofimenko,⊥ Stefan Mecking,‡ Maurice Brookhart,§ and Pedro J. Pe´rez ...
The complex Tp(Br3)Cu(NCMe) (1) is an excellent catalyst for the regioselective carbene transfer ... more The complex Tp(Br3)Cu(NCMe) (1) is an excellent catalyst for the regioselective carbene transfer reaction to tertiary C-H bonds of hydrocarbons, at room temperature, using the readily available ethyl diazoacetate (EDA) as the carbene source.
Diazocompounds have been extensively employed as a carbene source in organic synthesis. In the pa... more Diazocompounds have been extensively employed as a carbene source in organic synthesis. In the past decade, the incorporation of such fragments to a variety of substrates has been accomplished in many cases with the aid of an appropriate transition-metal complex acting as catalyst. 2 It is well-established that this transformation occurs via an electrophilic metallocarbene intermediate, although this species has only been detected once. 4 As shown in Scheme 1, the transfer of the carbene unit to a nucleophile affords the desired product and releases the metal center to reinitiate the catalytic cycle. The main drawback of this methodology is the existence of an undesirable side reaction, the homocoupling of the diazocompound (Scheme 1, left). This problem has been usually overcome by using slow addition devices and/or using excess of the nucleophilic substrate. The vast majority of systems capable of mediating this reaction bear nitrogen-donor ligands, 1 and they all display a similar behavior: ethyl diazoacetate is readily converted into diethyl fumarate and maleate because of this unwanted side reaction. On the other hand, phosphorus-containing ligands are not useful for this chemistry because of the facile carbene transfer to phosphorus to produce ylide derivatives.
A simple copper-based catalytic system has been developed for the carbon-hydrogen amidation react... more A simple copper-based catalytic system has been developed for the carbon-hydrogen amidation reaction. The copper-homoscorpionate complex Tp(Br3)Cu(NCMe) catalyzes the transfer of the nitrene unit NTs (Ts = p-toluenesulfonyl) and its subsequent insertion into the sp(3) C-H bonds of alkyl aromatic and cyclic ethers or the sp(2) C-H bonds of benzene using PhI=NTs as the nitrene source, affording the corresponding trisubstitued NR(1)HTs amines in moderate to high yields. The use of the environmentally friendly chloramine-T has also proven effective, with the advantage that sodium chloride is formed as the only byproduct. A tandem, one-pot consecutive nitrene-carbene insertion system has been developed to yield amino acid derivatives.
complexes as useful catalysts in the addition and/or insertion reaction of ethyl diazoacetate to ... more complexes as useful catalysts in the addition and/or insertion reaction of ethyl diazoacetate to saturated or unsaturated substrates; 31 refs.]. -(DIAZ-REQUEJO, M. M.; PEREZ, P. J.; J. Organomet. Chem. 690 (2005) 24-25, 5441-5450; Lab. Catal. Homogenea, Dep. Quim. Cienc. Mater., Univ. Huelva, E-21007 Huelva, Spain; Eng.) -Klein 25-233
The selectivity of the cyclopropanation of olefins with ethyl phenyldiazoacetate has been tested ... more The selectivity of the cyclopropanation of olefins with ethyl phenyldiazoacetate has been tested using different gold complexes bearing phosphine, phosphite or N-heterocyclic as ligands. A comparative study with related copper and silver complexes as catalysts is also presented.
Even in the context of hydrocarbons&a... more Even in the context of hydrocarbons' general resistance to selective functionalization, methane's volatility and strong bonds pose a particular challenge. We report here that silver complexes bearing perfluorinated indazolylborate ligands catalyze the reaction of methane (CH(4)) with ethyl diazoacetate (N(2)CHCO(2)Et) to yield ethyl propionate (CH(3)CH(2)CO(2)Et). The use of supercritical carbon dioxide (scCO(2)) as the solvent is key to the reaction's success. Although the catalyst is only sparingly soluble in CH(4)/CO(2) mixtures, optimized conditions presently result in a 19% yield of ethyl propionate (based on starting quantity of the diazoester) at 40°C over 14 hours.
ABSTRACT A series of complexes Tp(x)Cu (Tp(x) = homoscorpionate ligand) have been tested as the c... more ABSTRACT A series of complexes Tp(x)Cu (Tp(x) = homoscorpionate ligand) have been tested as the catalysts for the olefin aziridination reaction using PhINTs as the nitrene source. Very high yields of aziridines have been obtained with a group of representative substrates, including nonactivated terminal olefins. The high activity of these catalysts has allowed the use of equimolar amounts of PhINTs and olefins, avoiding the requirement of excess olefin. In an effort to eliminate nondesired byproducts, chloramine-T has been employed as the nitrene source, in a reaction that produces sodium chloride as the sole residue, with high degrees of conversions also being obtained.
Kinetic studies of the ethyl diazoacetate (EDA) decomposition reaction in the presence of BpCu (1... more Kinetic studies of the ethyl diazoacetate (EDA) decomposition reaction in the presence of BpCu (1) and in the presence or absence of olefin have led to the determination of several kinetic and thermodynamic parameters, and a consistent mechanism has been proposed for the olefin cyclopropanation reaction. Related studies with the complexes [Cu(bipy) 2 ]I (bipy ) bipyridine) and [Cu(bis(oxazoline)) 2 ]OTf have shown strong similarities with the results obtained with 1. A general mechanism covering the copper-based systems reported in the literature has been proposed, the real catalyst (i.e., the species to be reacted with EDA) in all cases being a neutral, 14-electron fragment of composition (L-L)Cu (L-L ) Bp-and Tp-like ligands, semicorrins, salicylaldehyde derivatives) or, alternatively, the isoelectronic, cationic [(L-L)Cu] + (for L-L ) bis(oxazoline), bipyridine). (22) kobsd values were calculated by means of kobsd ) (1/t) ln([EDA]0/ [EDA]). 17
Carbon-halogen (C-X) bonds (X=Cl, Br) can be easily functionalized with ethyl diazoacetate (N 2 C... more Carbon-halogen (C-X) bonds (X=Cl, Br) can be easily functionalized with ethyl diazoacetate (N 2 CHCO 2 Et) in the presence of silver-based catalysts containing the Tp x Ag core (Tp x = hydrotrispyrazolylborate ligand). Polyhalomethanes are converted into products derived from the formal insertion of the carbene CHCO 2 Et units into the C-X bond. In the case of monohaloalkanes (C 4 -C 6 ), cleavage of the C-X bond is observed, with formation of XCH 2 CO 2 Et and the corresponding olefin. Experimental evidence and theoretical calculations have led to the proposal of a novel mechanism to account for these transformations, in which the metal participates along the pathway in all the reaction steps. Among the experimental data, the first example of a metal-induced, asymmetric functionalization of a C-Cl bond by carbene insertion is included (ee=14 ( 2%). (36) Drudis-Sole, G.; Maseras, F.; Lledos, A.; Vallribera, A.; Moreno-Manas, M. Eur. J. Org. Chem. 2008, 5614.
Copper complexes containing chiral N-heterocyclic carbene ligands catalyze the regioselectiVe nuc... more Copper complexes containing chiral N-heterocyclic carbene ligands catalyze the regioselectiVe nucleophilic boryl attack at the -carbon of R, -unsaturated esters with enantioselectiVities up to 74% ee, depending on the nature of the ester group.
The complexes [Tp Br3 Ag] 2 ‚CH 3 COCH 3 (1) and Tp Br3 Ag(thf) (2) catalyze the insertion of the... more The complexes [Tp Br3 Ag] 2 ‚CH 3 COCH 3 (1) and Tp Br3 Ag(thf) (2) catalyze the insertion of the :CHCO 2 Et group from ethyl diazoacetate (EDA) into the saturated C-H bonds of several C5, C6, and C8 linear and branched alkanes. In addition to secondary and/or tertiary sites, the unprecedented insertion into the primary C-H bonds of the substrates studied has been observed with variable regioselectivity, toward the methyl groups, within the range of 40-60% for branched and nearly 25% for linear alkanes.
Facile alkane functionalization by means of the insertion of :CHCO 2 Et, from ethyl diazoacetate,... more Facile alkane functionalization by means of the insertion of :CHCO 2 Et, from ethyl diazoacetate, into carbon-hydrogen bonds mediated by catalytic amounts of (NHC)MCl (NHC ) N-heterocyclic ligand; M ) Cu, Au) and a halide scavenger MX has been achieved. This chemistry includes the insertion of the carbene fragment into alkane primary positions with Cu-and Au-based catalysts. The nature of the counterion X and of the NHC ligand have a significant effect on the overall yields and regioselectivity of the reaction.
Since its discovery in the late 1970s, Rh 2 (OAc) 4 has been the catalyst of choice for the above... more Since its discovery in the late 1970s, Rh 2 (OAc) 4 has been the catalyst of choice for the above transformations. 5 This complex catalyzes the insertion of several diazo compounds 6,7 into the O−H bond of saturated alcohols at room temperature and in high yield. Other metals ...
The reaction of benzene and ethyl diazoacetate under thermal or photochemical conditions was repo... more The reaction of benzene and ethyl diazoacetate under thermal or photochemical conditions was reported by Büchner almost a century ago. 1 The mixture of cycloheptatrienes obtained in that way was formed upon the formal addition of a carbene group to a double bond of ...
DFT Becke3LYP calculations are applied to the computational study of the activation of alkane C−H... more DFT Becke3LYP calculations are applied to the computational study of the activation of alkane C−H bonds by metallocarbene homoscorpionate complexes. A total of 16 different combinations of metallocarbene complex and alkane are explored, defined by the use of TpAg C(H)(CO ...
Complexes of general formula Tp x Cu (Tp x = homoscorpionate ligand) have been employed as cataly... more Complexes of general formula Tp x Cu (Tp x = homoscorpionate ligand) have been employed as catalysts for the insertion of ethyl diazoacetate into C−H bonds of a variety of hydrocarbons and ethers, in moderate to high yields: tertiary, secondary, and primary C−H bonds have ...
The complex {[HC(3,5-Me 2 pz) 3 ]Cu(NCMe)}BF 4 catalyzes the transfer of the :CHCO 2 Et unit from... more The complex {[HC(3,5-Me 2 pz) 3 ]Cu(NCMe)}BF 4 catalyzes the transfer of the :CHCO 2 Et unit from ethyl diazoacetate to several saturated and unsaturated substrates with very high yields and under biphasic conditions using the ionic liquid [bmim][PF 6 ] and hexane as the reaction medium. The catalyst has been tested for several cycles of recovery and reuse without any loss of activity.
Page 1. Controlled, Copper-Catalyzed Functionalization of Polyolefins M. Mar Dı´az-Requejo,† Pete... more Page 1. Controlled, Copper-Catalyzed Functionalization of Polyolefins M. Mar Dı´az-Requejo,† Peter Wehrmann,‡ Mark D. Leatherman,§ Swiatoslaw Trofimenko,⊥ Stefan Mecking,‡ Maurice Brookhart,§ and Pedro J. Pe´rez ...
The complex Tp(Br3)Cu(NCMe) (1) is an excellent catalyst for the regioselective carbene transfer ... more The complex Tp(Br3)Cu(NCMe) (1) is an excellent catalyst for the regioselective carbene transfer reaction to tertiary C-H bonds of hydrocarbons, at room temperature, using the readily available ethyl diazoacetate (EDA) as the carbene source.
Diazocompounds have been extensively employed as a carbene source in organic synthesis. In the pa... more Diazocompounds have been extensively employed as a carbene source in organic synthesis. In the past decade, the incorporation of such fragments to a variety of substrates has been accomplished in many cases with the aid of an appropriate transition-metal complex acting as catalyst. 2 It is well-established that this transformation occurs via an electrophilic metallocarbene intermediate, although this species has only been detected once. 4 As shown in Scheme 1, the transfer of the carbene unit to a nucleophile affords the desired product and releases the metal center to reinitiate the catalytic cycle. The main drawback of this methodology is the existence of an undesirable side reaction, the homocoupling of the diazocompound (Scheme 1, left). This problem has been usually overcome by using slow addition devices and/or using excess of the nucleophilic substrate. The vast majority of systems capable of mediating this reaction bear nitrogen-donor ligands, 1 and they all display a similar behavior: ethyl diazoacetate is readily converted into diethyl fumarate and maleate because of this unwanted side reaction. On the other hand, phosphorus-containing ligands are not useful for this chemistry because of the facile carbene transfer to phosphorus to produce ylide derivatives.
A simple copper-based catalytic system has been developed for the carbon-hydrogen amidation react... more A simple copper-based catalytic system has been developed for the carbon-hydrogen amidation reaction. The copper-homoscorpionate complex Tp(Br3)Cu(NCMe) catalyzes the transfer of the nitrene unit NTs (Ts = p-toluenesulfonyl) and its subsequent insertion into the sp(3) C-H bonds of alkyl aromatic and cyclic ethers or the sp(2) C-H bonds of benzene using PhI=NTs as the nitrene source, affording the corresponding trisubstitued NR(1)HTs amines in moderate to high yields. The use of the environmentally friendly chloramine-T has also proven effective, with the advantage that sodium chloride is formed as the only byproduct. A tandem, one-pot consecutive nitrene-carbene insertion system has been developed to yield amino acid derivatives.
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