489431-30-3Relevant academic research and scientific papers
Ru-Based Catechothiolate Complexes Bearing an Unsaturated NHC Ligand: Effective Cross-Metathesis Catalysts for Synthesis of (Z)-α,β-Unsaturated Esters, Carboxylic Acids, and Primary, Secondary, and Weinreb Amides
Liu, Zhenxing,Xu, Chaofan,Del Pozo, Juan,Torker, Sebastian,Hoveyda, Amir H.
supporting information, p. 7137 - 7146 (2019/05/10)
Despite notable progress, olefin metathesis methods for preparation of (Z)-α,β-unsaturated carbonyl compounds, applicable to the synthesis of a large variety of bioactive molecules, remain scarce. Especially desirable are transformations that can be promoted by ruthenium-based catalysts, as such entities would allow direct access to carboxylic esters and amides, or acids (in contrast to molybdenum-or tungsten-based alkylidenes). Here, we detail how, based on the mechanistic insight obtained through computational and experimental studies, a readily accessible ruthenium catechothiolate complex was found that may be used to generate many α,β-unsaturated carbonyl compounds in up to 81% yield and ≥98:2 Z/E ratio. We show that through the use of a complex bearing an unsaturated N-heterocyclic carbene (NHC) ligand, for the first time, products derived from the more electron-deficient esters, acids, and Weinreb amides (vs primary or secondary amides) can be synthesized efficiently and with high stereochemical control. The importance of the new advance to synthesis of bioactive compounds is illustrated through two representative applications: An eight-step, 15% overall yield, and completely Z-selective route leading to an intermediate that may be used in synthesis of stagonolide E (vs 11 steps, 4% overall yield and 91% Z, previously), and a five-step, 25% overall yield sequence to access a precursor to dihydrocompactin (vs 13 steps and 5% overall yield, formerly).
Application of organocerium reagents for the efficient conversion of Z-α,β-unsaturated Weinreb amides to Z-α,β-unsaturated ketones
Kojima, Satoshi,Hidaka, Tsugihiko,Yamakawa, Atsushi
, p. 470 - 471 (2007/10/03)
The reactions of Z-rich unsaturated Weinreb amides with organolithium and organocerium reagents were examined. Taking in consideration both the extent of geometry retention and cleanness of the reaction, organocerium reagents were more effective for the conversion to Z-α,β-unsaturated ketones. Copyright
Synthesis of β-monosubstituted α,β-unsaturated amides with z-selectivity using diphenylphosphonoacetamides
Kojima, Satoshi,Hidaka, Tsugihiko,Ohba, Yuko
, p. 515 - 523 (2007/10/03)
The utility of diphenylphosphonoacetamides [(PhO)2P(O)CH 2CONRR′] as Horner-Wadsworth-Emmons reagents was examined with five different patterns of substitution upon the amide nitrogen atom (2a: R, R′ = CH2Ph; 2b: R = CH2Ph, R′ = H; 2c: R = Me, R′ = OMe; 2d: R, R′ = Ph; 2e: R, R′ = (CH2) 4). The reaction of 2a was found to be Z-selective for aromatic aldehydes with selectivities up to 95:5. Reagent 2b led to reasonable selectivity for both benzaldehyde (85:15) and 3-phenylpropionaldehyde (87:13), while 2c was somewhat effective for only the latter alkyl aldehyde (83:17). Compounds 2d and 2e exhibited slightly lower selectivities compared with 2a.
