68622-84-4Relevant academic research and scientific papers
An Amine-Assisted Ionic Monohydride Mechanism Enables Selective Alkyne cis-Semihydrogenation with Ethanol: From Elementary Steps to Catalysis
Huang, Zhidao,Wang, Yulei,Leng, Xuebing,Huang, Zheng
supporting information, p. 4824 - 4836 (2021/04/07)
The selective synthesis of Z-alkenes in alkyne semihydrogenation relies on the reactivity difference of the catalysts toward the starting materials and the products. Here we report Z-selective semihydrogenation of alkynes with ethanol via a coordination-induced ionic monohydride mechanism. The EtOH-coordination-driven Cl- dissociation in a pincer Ir(III) hydridochloride complex (NCP)IrHCl (1) forms a cationic monohydride, [(NCP)IrH(EtOH)]+Cl-, that reacts selectively with alkynes over the corresponding Z-alkenes, thereby overcoming competing thermodynamically dominant alkene Z-E isomerization and overreduction. The challenge for establishing a catalytic cycle, however, lies in the alcoholysis step; the reaction of the alkyne insertion product (NCP)IrCl(vinyl) with EtOH does occur, but very slowly. Surprisingly, the alcoholysis does not proceed via direct protonolysis of the Ir-C(vinyl) bond. Instead, mechanistic data are consistent with an anion-involved alcoholysis pathway involving ionization of (NCP)IrCl(vinyl) via EtOH-for-Cl substitution and reversible protonation of Cl- ion with an Ir(III)-bound EtOH, followed by β-H elimination of the ethoxy ligand and C(vinyl)-H reductive elimination. The use of an amine is key to the monohydride mechanism by promoting the alcoholysis. The 1-amine-EtOH catalytic system exhibits an unprecedented level of substrate scope, generality, and compatibility, as demonstrated by Z-selective reduction of all alkyne classes, including challenging enynes and complex polyfunctionalized molecules. Comparison with a cationic monohydride complex bearing a noncoordinating BArF- ion elucidates the beneficial role of the Cl- ion in controlling the stereoselectivity, and comparison between 1-amine-EtOH and 1-NaOtBu-EtOH underscores the fact that this base variable, albeit in catalytic amounts, leads to different mechanisms and consequently different stereoselectivity.
Straightforward synthesis of phenanthrenes from styrenes and arenes
Li, Hu,He, Ke-Han,Liu, Jia,Wang, Bi-Qin,Zhao, Ke-Qing,Hu, Ping,Shi, Zhang-Jie
supporting information; experimental part, p. 7028 - 7030 (2012/08/07)
Semi-one-pot synthesis of phenanthrenes from styrenes and arenes was developed through cross-dehydrogenative coupling. A sequence of Heck-type coupling and photo-cyclization were involved and a variety of functionalities were tolerated. This method provides an effective and practical protocol towards the synthesis of substituted phenanthrenes. The Royal Society of Chemistry 2012.
Palladium-catalyzed annulation of 1,2-diborylalkenes and -arenes with 1-bromo-2-[(Z)-2-bromoethenyl]arenes: A modular approach to multisubstituted naphthalenes and fused phenanthrenes
Shimizu, Masaki,Tomioka, Yosuke,Nagao, Ikuhiro,Kadowaki, Tsugumi,Hiyama, Tamejiro
scheme or table, p. 1644 - 1651 (2012/09/08)
(Z)-1,2-Diaryl-1,2-bis(pinacolatoboryl)ethenes underwent double-cross-coupling reactions with 1-bromo-2-[(Z)-2-bromoethenyl]arenes in the presence of [Pd(PPh3)4] as a catalyst and 3 M aqueous Cs2CO3 as a base in THF at 80 °C. The double-coupling reaction gave multisubstituted naphthalenes in good to high yields. Annulation of 1,2-bis(pinacolatoboryl)arenes with bromo(bromoethenyl)arenes in the presence of a catalyst system that consisted of [Pd2(dba)3] (dba=dibenzylideneacetone) and 2-dicyclohexylphosphino-2′,6′- dimethoxybiphenyl (SPhos) under the same conditions produced fused phenanthrenes in good to high yields. The first annulation coupling occurred regiospecifically at the bromoethenyl moiety. This procedure is applicable to the facile synthesis of polysubstituted anthracenes, benzothiophenes, and dibenzoanthracenes through a double annulation pathway by using the corresponding dibromobis[(Z)-2-bromoethenyl]benzenes as diboryl coupling partners. Copyright
Suzuki-Miyaura cross-coupling of aryl carbamates and sulfamates: Experimental and computational studies
Quasdorf, Kyle W.,Antoft-Finch, Aurora,Liu, Peng,Silberstein, Amanda L.,Komaromi, Anna,Blackburn, Tom,Ramgren, Stephen D.,Houk,Snieckus, Victor,Garg, Neil K.
scheme or table, p. 6352 - 6363 (2011/06/19)
The first Suzuki-Miyaura cross-coupling reactions of the synthetically versatile aryl O-carbamate and O-sulfamate groups are described. The transformations utilize the inexpensive, bench-stable catalyst NiCl 2(PCy3)2 to furnish biaryls in good to excellent yields. A broad scope for this methodology has been demonstrated. Substrates with electron-donating and electron-withdrawing groups are tolerated, in addition to those that possess ortho substituents. Furthermore, heteroaryl substrates may be employed as coupling partners. A computational study providing the full catalytic cycles for these cross-coupling reactions is described. The oxidative addition with carbamates or sulfamates occurs via a five-centered transition state, resulting in the exclusive cleavage of the aryl C-O bond. Water is found to stabilize the Ni-carbamate catalyst resting state, which thus provides rationalization of the relative decreased rate of coupling of carbamates. Several synthetic applications are presented to showcase the utility of the methodology in the synthesis of polysubstituted aromatic compounds of natural product and bioactive molecule interest.
Stereoselective addition of diphenylphosphine to substituted diphenylethynes: Synthetic, NMR and X-ray crystallographic studies
Bookham, Jonathan L.,Smithies, Darren M.,Wright, Anna,Thornton-Pett, Mark,McFarlane, William
, p. 811 - 818 (2007/10/03)
The base-catalysed addition of diphenylphosphine to the substituted diphenylethynes RC≡CR′ (R = Ph, R′ = Ph, o-tolyl, m-tolyl or 2-biphenyl; R = m-tolyl, R′ = o-tolyl or m-tolyl) yielded Ph2PC(R)=CHR′ and/or Ph2PCH(R)CH(R′)PPh2. Proton, 13C, 13P and two-dimensional rotating frame Overhauser enhancement 1H NMR spectra have been used to determine the stereochemical pathways of the reactions and the stereochemistry of the products. In general the more hindered alkynes undergo monoaddition ultimately to yield phosphinoalkenes with the Ph2P attached to the carbon bearing the least bulky substituent and cis to the olefinic proton, while for the less hindered alkynes the trans isomer is formed initially and this then reacts further to give mesolerythro-diphosphinoalkanes. Bis(o-tolyl)ethyne does not react with Ph2PH under the same conditions. Crystal structures were determined for E- and Z-Ph2P(Ph)C=CHPh and show distortions of interbond angles consistent with the pattern of strain implied by the foregoing reactions. The sulfides of the phosphinoalkenes and the Mo(CO)4 complexes of the diphosphinoalkanes were also prepared and their 1H, 13C and 31P NMR spectra recorded. In several cases the pattern of 13CO NMR signals for the complexes was used unambiguously to determine the stereochemistry of the parent diphosphines.
Regiochemistry and Stereochemistry of Nickel-Promoted, Carbon-Carbon Bond-Forming Reactions of Cyclic Sulfur Compounds
Tiecco, Marcello,Tingoli, Marco,Wenkert, Ernest
, p. 3828 - 3831 (2007/10/02)
Reaction of methylmagnesium iodide and phenylmagnesium bromide with thianaphthene, dibenzothiophenone, thianthrene, and 2,3-dihydrothiapyran in the presence of nickel dichloride have been shown to yield, regioselectively in most cases, ring-opened products in which the carbon-sulfur bonds have been replaced by carbon-carbon bonds.Stereospecific carbon-carbon bond formation has taken place in the reactions of thianaphthene and 2,3-dihydrothiapyran, the products having maintained the cis-olefin configuration of the starting sulfur compounds.Isomerization into the more stable compounds has been observed in some cases.
