14740-77-3Relevant academic research and scientific papers
Unexpected reactivity of pyridinium salts toward alkynyl Fischer complexes to produce oxo-heterocycles
Flores-Conde, María Inés,de la Cruz, Fabiola N.,López, Julio,Jiménez-Halla, J. óscar C.,Pe?a-Cabrera, Eduardo,Flores-álamo, Marcos,Delgado, Francisco,Vázquez, Miguel A.
, (2017/12/28)
The unprecedented reaction of ketone-containing aromatic pyridinium salts 3a-e and alkynyl Fischer complexes 1a-f proceeds via a mild domino process to provide 4,6-disubstituted pyran-2-ones 5a-k and 2,3,5-trisubstituted furans 6a-h (45-97%). According of the results of isotopic labeling experiments, a mechanism involving an initial Michael addition appears to be the key step, obtaining a mesomeric structure responsible for the formation of both products.
Chemoselective stepwise demetalation of unusually stable fischer biscarbene complexes by domino [4+2]/[2+2] cycloaddition of 2-isopropenyl-2-oxazoline to 1-alkynyl Fischer carbene complexes of chromium and tungsten
Chen, Jinzhu,Yu, Zhengkun,Zheng, Zhaoyan,Gu, Kaichun,Wu, Sizhong,Zeng, Fanlong,Tan, Weiqiang,Wu, Xiaowei,Xiao, Wenjing
, p. 302 - 308 (2008/10/09)
Domino [4+2]/[2+2] cycloaddition of 2-isopropenyl-2-oxazoline 2 to 1-alkynyl Fischer carbene complexes (CO)5M=C(OEt)C=CPh 1 (a, M = Cr; b, W) in a 1:2 molar ratio afforded unusually stable biscarbene complexes 3a and 3b containing a novel four-, five-, and six-membered tricyclic core in 99.6% and 45.2% yields, respectively. Chain-opening β-aminoalkenyl monocarbene complex 4b and β-amidoalkenyl monocarbene complex 5b of tungsten were also isolated from the cycloaddition upon treatment of the reaction mixture of 1b and 2 on silica gel. Partial and full oxidation of 3a,b with pyridine N-oxide underwent efficient chemoselective stepwise demetalation to afford the corresponding monocarbene complexes 6a,b and organic diester 7, respectively, under mild conditions. The X-ray crystallographic study revealed the presence of a four-, five-, and six-membered tricyclic core in compounds 3,6, and 7, and the methyl and oxazolindinyl groups derived from oxazoline 2 are positioned syn with respect to the azabicyclo[4.2.0]octadiene bicyclic moiety, which is oriented in the opposite direction. X-ray crystal structural data are reported for the bis- and monocarbene complexes 3a, 5b, and 6b as well as for diester 7.
Four-coordinate group-14 elements in the formal oxidation state of zero - Syntheses, structures, and dynamics of [{(CO)5Cr}2Sn(L2)] and related species
Kircher, Peter,Huttner, Gottfried,Heinze, Katja,Schiemenz, Berthold,Zsolnai, Laszlo,Buechner, Michael,Driess, Alexander
, p. 703 - 720 (2007/10/03)
The sodium salts Na2[{(CO)5M}2EX2] (M = Cr, Mo, W; E = Ge, Sn, Pb; X = Cl, I, OOCCH3) react with 2,2′-bipyridine (bipy) to form neutral compounds [{(CO)5M}2E(bipy)] (E = Sn: 1a-1c; E = Ge: 3a; E = Pb: 4). 1,10-Phenanthroline (phen) analogues of compounds 1a-1c and 3a [{(CO)5M}2E(phen)] (E = Sn: 1d-1f, E = Ge: 3b) are as well accessible. The 2,2′-bipyridine ligand in 1 may be formally replaced by two pyridine (py) ligands resulting in [{(CO)5M}2Sn(py)2] (1g: M = Cr, 1h: M = W). The bis-bidentate ligand 2,2′-bipyrimidine (bpmd) is found to coordinate just one [{(CO)5M}2Sn] entity in [{(CO)5M}2Sn(bpmd)] (2b: M = Cr, 2c: M = W). The biimidazolato (biim) ligand binds two [{(CO)5Cr}2Sn] moieties in [{(CO)5Cr}2Sn(biim)Sn{Cr(CO)5} 2]2-, 2a. It is shown by 1H-NMR that the pyrimidine entities in these compounds (2b, 2c) are able to rotate by a full 180° turnaround with respect to one another. This process must involve complete de-coordination of at least one of the two nitrogen donors in again at least one of the chelate cycles, the activation energy for this process being around 60 kJ/ mol. By 119Sn-NMR spectroscopy of almost all of the tin compounds described it is shown that equilibria between [{(CO)5M}2Sn(L2)] and [{(CO)5M}2Sn(L)] + L exist in all cases. From the temperature dependence of the δ values it is concluded that the activation barriers for this association/ dissociation process is below 10 kJ/mol. The structures of all new compounds are documented by X-ray analyses and all compounds are characterized by the usual analytical and spectroscopical techniques.
Photochemistry of (η6-2,6-X2C5H3 N)Cr(CO)3 (X = H, CH3, (CH3)3Si). First example of a photoinduced ring-slip at an (η6-arene)M(CO)3 center.
Breheny, Ciara J.,Draper, Sylvia M.,Grevels, Friedrich-W.,Klotzbücher, Werner E.,Long, Conor,Pryce, Mary T.,Russell, Graham
, p. 3679 - 3687 (2008/10/08)
The photochemistry of (η6-2,6-X2C5H3N)Cr(CO) 3 was investigated both in low-temperature matrices (X = H or (CH3)3Si) and in room-temperature solution (X = H, CH3, or (CH3)3 Si), Room-temperature photolysis (λexc > 410 nm) in CO-saturated methanol or acetonitrile produced (η1-2,6-X2C5H3N)Cr(CCO) 5 which subsequently formed Cr(CO)6 in a secondary photochemical process (X = H or CH3), The efficiency of pentacarbonyl formation is lower in CO-saturated cyclohexane and follows the order X = H > X = CH3, Photolysis in low-temperature matrices resulted in an η6 to η1 pyridine ring-slippage (λexc = 460 nm; X = H). Visible irradiation in a CO-doped methane matrix produced (η1-C5H5N)Cr(CO)5, while in an N2 matrix fac-(η1-C5H5N)N2 2Cr(CO)3 is formed. Irradiation with λexc = 308 nm produced both the ring-slippage product and also the CO-loss product (η6-C5H5)Cr(CO)2, which in a N2 matrix is trapped as (η6- C5H5N)Cr(CO)2(N2). Time-resolved infrared spectroscopy in cyclohexane revealed only the CO-loss product (λexc = 308 nm; X = H). The apparent difference in room-temperature and low-temperature photochemistry is explained by a rapid regeneration of (η6- C5H5N)Cr(CO)3 from the η1-intermediate. This explanation was supported by laser flash photolysis experiments (λexc = 355 nm) in CO-saturated cyclohexane (Sol), where the recovery of the (η6- C5H5N)Cr(CO)3 absorption follows a biphasic time profile, whereby the faster process was assigned to the η1 to η6 transformation and the slower to the reaction Of (η6- C5H5N)Cr(CO)2(Sol) with CO. Crystals of (η6-2,6-(CH3)2C5H 3N)Cr(CO)3 and (η6-2,6-((CH3)3Si)2C 5H3N)Cr(CO)3 were characterized by X-ray diffraction.
Organic Syntheses with Transition Metal Complexes, 48. - Methyl Thiocarbene and Alkenyl Thiocarbene Chromium Complexes: Synthesis and Reactions
Aumann, Rudolf,Schroeder, Jochen
, p. 2053 - 2058 (2007/10/02)
Thiocarbene chromium complexes (CO)5Cr=C(SR1)R (4: R = Me, Ph; R1 = c-C6H11, CH2CH=CH2, C2H5, C6H5) were readily obtained in up to 97 percent isolated yields from the corresponding ethoxycarbene chromium complexes 5a,b and thiols 6 in methanol in the presence of Na2CO3 as a catalyst.Reaction conditions, which lead to unfavorable side products, like thioacetals 8 and/or thioenol ether 10, are discussed.Methyl thiocarbene complexes 4b-d undergo a facile aldol condensation with the aromatic aldehydes 14 or 16 to give alkenyl thiocarbene complexes 15b-d and 17, respectively.The Cr=C bonds of 15 prove to be reactive towards the insertion of isocyanides or oxygen.Thus, on addition of two equivalents of the isocyanide 18 to 15d, 1-aza-1,2,4-pentatriene 20 is obtained.The oxidative decomposition of 15d on silica gel leads to the formation of thioester 25 and thioindene 26.Characteristic differences in the reactivity of thiocarbene complexes and ethoxycarbene complexes are discussed.
Organic Syntheses via Transition Metal Complexes, 25. - Cyanoallylation of Carbene Ligands with Allyl Isocyanides via Metal-Induced N/C-Allylic Rearrangement of Intermediate 3-Aza-1,2,5-hexatriene Complexes
Aumann, Rudolf,Kuckert, Eberhard,Heinen, Heinrich
, p. 1293 - 1296 (2007/10/02)
Allyl isocyanides 2 react with (CO)5M=C(OEt)C6H5 (1, M = Cr, W) to give N-allylketenimine/(3-aza-1,2,5-hexatriene) complexes 3 in high yields.In absence of suitable reactants compounds 3 isomerise spontaneously and smoothly already at 0 deg C via a metal-induced N/C-migration of the allyl group to give 4-pentenenitrile complexes 5, from which the ligand can be disengaged by substitution with pyridine.The regiochemistry of the rearrangement corresponds to the type as has been proven by a labeling experiment with α,α-dideuterioallyl isocyanide.In the presence of an alcohol, the reaction of 1 with 2 leads to the formation of competition products resulting from an N/C-rearrangement or the addition of the alcohol to 3, respectively.The competition ratio strongly depends on the type of metal used.The tungsten complex 3b, e.g., at 0 deg C adds one equivalent of an alcohol to give up to 97percent yields of (allylamino)carbene complexes 8b-c, while the corresponding chromium complex 3a rearranges smoothly under these conditions to give 5a only.The addition of alcohols to 3b is reversible: on thermolysis of 8c at 70 deg C the products of thermal isomerisation of 3b together with a chelate complex 9 are obtained.
