19706-05-9Relevant academic research and scientific papers
Comparative measure of the electronic influence of highly substituted aryl isocyanides
Carpenter, Alex E.,Mokhtarzadeh, Charles C.,Ripatti, Donald S.,Havrylyuk, Irena,Kamezawa, Ryo,Moore, Curtis E.,Rheingold, Arnold. L.,Figueroa, Joshua S.
supporting information, p. 2936 - 2944 (2015/03/30)
To assess the relative electronic influence of highly substituted aryl isocyanides on transition metal centers, a series of C4v-symmetric Cr(CNR)(CO)5 complexes featuring various alkyl, aryl, and m-terphenyl substituents have been prepared. A correlation between carbonyl-ligand 13C{1H} NMR chemical shift (δCO) and calculated Cotton-Kraihanzel (C-K) force constant (kCO) is presented for these complexes to determine the relative changes in isocyanide σ-donor/π-acid ratio as a function of substituent identity and pattern. For nonfluorinated aryl isocyanides possessing alkyl or aryl substitution, minimal variation in effective σ-donor/π-acid ratio is observed over the series. In addition, aryl isocyanides featuring strongly electron-releasing substituents display an electronic influence that nearly matches that of nonfluorinated alkyl isocyanides. Lower σ-donor/π-acid ratios are displayed by polyfluorinated aryl isocyanide ligands. However, the degree of this attenuation relative to nonfluorinated aryl isocyanides is not substantial and significantly higher σ-donor/π-acid ratios than CO are observed in all cases. Substituent patterns for polyfluorinated aryl isocyanides are identified that give rise to low relative σ-donor/π-acid ratios but offer synthetic convenience for coordination chemistry applications. In order to expand the range of available substitution patterns for comparison, the syntheses of the new m-terphenyl isocyanides CNArTripp2, CNp-MeArMes2, CNp-MeArDArF2, and CNp-FArDArF2 are also reported (ArTripp2 = 2,6-(2,4,6-(i-Pr)3C6H2)2C6H3); p-MeArMes2 = 2,6-(2,4,6-Me3C6H2)2-4-Me-C6H2); p-MeArDArF2 = 2,6-(3,5-(CF3)2C6H3)2-4-Me-C6H2); p-FArDArF2 = 2,6-(3,5-(CF3)2C6H3)2-4-F-C6H2).
Synthesis of Isonitrile Complexes of Group-VI Metal Carbonyls and Their Use as Mediator in the [2+2+2]-Cyclization of Alkynes
Sugihara, Takumichi,Yamada, Mamiko,Nishizawa, Mugio
, p. 645 - 647 (2007/10/03)
A method for selective synthesis of metal carbonyl complexes with certain number of isonitriles has been introduced. The use of these complexes as a mediator in the partially intermolecular [2+2+2]-cyclic cotrimerization of alkynes has also been demonstrated.
Organic Syntheses via Transition Metal Complexes, 64. - 1,4-Diaminonaphthalines via Ketenimine Complexes from (β-Aminovinylcarbene)chromium Complexes and Isocyanides
Aumann, Rudolf
, p. 1867 - 1872 (2007/10/02)
The thermal reaction of (dienylcarbene)chromium complexes (= 1-chroma-1,3,5-trienes) with isocyanides provides a mild and regiospecific access to aromatic amines.Thus, 1,4-diamino-2-ethoxynaphthalines 6a-d 1=NMe2 (a), (S)-2-hydroxymethylpyrrolidinyl (b), (1R,2S)-2-methylamino-1-phenyl-1-propanol (c), NtBuMe (d)> are obtained by the cyclization of (E)-(β-aminostyrylcarbene)chomium complexes (CO)5Cr=C(OEt)CH=C(NRR1)C6H5 with cyclohexyl isocyanide (4) at 90 deg C in 72-85 percent.The aminocarbene complexes (E)-3a-d are accessible with high stereoselectivity 95 percent (E) configuration> and chemical yields of 91-96 percent by the addition of secondary amines HNRR1 2a-d to the (1-alkoxy-3-phenylpropynylidene)chromium complex (CO)5Cr=C(OEt)CCC6H5 (1). 3 and 4 give initially mono- and bis(isocyanide) complexes, e.g. (E)-8a and (E)-9a, and subsequently dienylketenimine complexes by the insertion of 4 into the M=C bond of 3.Dienylketenimine complexes are key intermediates in the formation of 6. - Key Words: Aminobenzannulation with isocyanides / 1,4-Diaminonaphthalines / Alkynylcarbene complexes / β-Aminovinylcarbene complexes / Dienylketenimine complexes / 4-Amino-1-chroma-1,3-dienes / Chromium complexes
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, 35. - (C-Amino)Ketene Imines, 2-Imidazolin-5-ones, and Α-Amino Acids from Aminocarbene Chromium Complexes and Isocyanides
Aumann, Rudolf,Heinen, Heinrich
, p. 1139 - 1146 (2007/10/02)
C-(Alkylideneamino)ketene imines (1,4-diaza-1,2,4-pentatrienes) 8 are easily accessible by C=C coupling of isocyanides R1-NC (2, R1 = t-C4H9, c-C6H11, CH3) with the (alkylideneamino)carbene (= 2-azaallenyl) ligand of (CO)5Cr-+=C(C6H5)OCOC6H5> (6).The tendency for an insertion of 2 into M=C bonds of aminocarbene complexes strongly depends on the electronic character of the aminocarbene ligand.Electron-rich aminocarbene chromium complexes like (CO)5Cr=C(NR2)C6H5 (1, R = H, CH3), show only little tendency for an insertion but mainly give cis-(R1-NC)(CO)4Cr=C(NR2)C6H5 (3) by susbtitution of CO.Electron-poor aminocarbene complexes like 6 (readily available on N-benzoylation of 1a) undergo a facile insertion of 2 into the M=C bond with smooth formation of 7.From 7 ketene imine 8 is spontaneously disengaged by a second equivalent of 2.The reaction works especially well with bulky isocyanides 2a, b.In the case of methyl isocyanide (2c) a chromium complex 15 is obtained as a minor product besides 8c. 15 results from a cycloaddition of 2c at the ketene imine ligand of 7c.C-(Alkylideneamino)ketene imines 8 are easily accessible by our method.They prove to be very thermolabile in solution and spontaneously isomerize to give 2-imidazolin-5-ones 10 and C-amidoketene imines 11.Under the influence of wet silica gel ketene imine derivatives 8 rapidly form α-amino acid amides 16 by hydrolysis with concomitant migration of a benzoyl group.Under the same conditions 11 also gives the "normal" α-amino acid amides 17. - Keywords: C-(Alkylideneamino)ketene imines; Isocyanides, C=C coupling with aminocarbene ligands; (2-Azaallenyl)chromium complexes; 2-Imidazolin-5-ones; α-Amino acids
SYNTHESIS OF THE PENTACARBONYL(CHALCOCARBONYL)CHROMIUM(0) COMPLEXES, Cr(CO)5(CX) (X = S, Se)
English, Ann M.,Plowman, Keith R.,Baibich, Ione M.,Hickey, James P.,Butler, Ian S.,et al.
, p. 177 - 183 (2007/10/02)
The arene complexes, (η6-C6H6)Cr(CO)2(CX) (X = S, Se), react with excess CO gas under pressure in tetrahydrofuran at about 60 deg C to produce the Cr(CO)5(CX) complexes in high yield.The IR and NMR (13C and 17O) spectra of these complexes are i
ISONITRILSYNTHESEN AM KOMPLEX V. DESULFURIERUNG VON ISOTHIOCYANATEN IN CARBONYLMETALLAT-ADDITIONS-VERBINDUNGEN
Fehlhammer, Wolf Peter,Mayr, Andreas
, p. 153 - 160 (2007/10/02)
The isocyanide complexes and Cr(CO)5CNR (R = CH3, C6H11, C6H5) are conveniently prepared at -50 deg C from carbonyl metallates, isothiocyanates, and phosgene.At room temperature Na reacts with isothiocyanates (1/
