72658-10-7Relevant academic research and scientific papers
Synthesis of α-Heteroaryl Propionic Esters by Palladium-Catalyzed α-Heteroarylation of Silyl Ketene Acetals
Li, Bowen,Luo, Bangke,Blakemore, Caroline A.,Smith, Aaron C.,Widlicka, Daniel W.,Berritt, Simon,Tang, Wenjun
, p. 6439 - 6443 (2021)
A practical and efficient synthesis of α-heteroaryl propionic esters is developed by employing palladium-catalyzed α-heteroarylation of silyl ketene acetals, forming a wide variety of α-heteroaryl propionic esters with various substituents and functionalities in high yields. The success of this transformation is credited to the development of the bulky P,P═O ligand. The method has provided an efficient synthesis of α-heteroaryl propionic acids.
Rh-Catalyzed reductive Mannich-type reaction and its application towards the synthesis of (±)-ezetimibe
Isoda, Motoyuki,Sato, Kazuyuki,Kunugi, Yurika,Tokonishi, Satsuki,Tarui, Atsushi,Omote, Masaaki,Minami, Hideki,Ando, Akira
, p. 1608 - 1615 (2016/10/05)
An effective synthesis for syn-β-lactams was achieved using a Rh-catalyzed reductive Mannich-type reaction. A rhodium-hydride complex (Rh-H) derived from diethylzinc (Et2Zn) and a Rh catalyst was used for the 1,4-reduction of an α,β-unsaturated ester to give a Reformatsky-type reagent, which in turn, reacted with an imine to give the syn-β-lactam. Additionally, the reaction was applied to the synthesis of (±)-ezetimibe, a potent β-lactamic cholesterol absorption inhibitor.
CHIRAL PHOSPHINES FOR PALLADIUM-CATALYZED ASYMMETRIC ALPHA-ARYLATION OF ESTER ENOLATES TO PRODUCE TERTIARY STEREOCENTERS IN HIGH ENANTIOSELECTIVITY
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Paragraph 00181-00182, (2013/03/26)
The disclosure provides new and improved methods for the Pd-catalyzed asymmetric α-arylation of ester compounds, which produce the corresponding α-aryl moiety in high enantioselectivity (generally >90% ee). The present methods utilize a palladium catalyst supported by new (R)-H8-BINOL-derived monophosphine ligands. The method is applicable to a wide variety of aryl triflate substrates having variations in both electronic and steric properties. These aryl triflate substrates react with various α-alkyl (Z)- and/or (E)-0-trimethylsilyl ketene acetals in the presence of a Pd catalyst, (R)-H8-BINOL-derived monophosphine ligand, and a mild activator, for example, LiOAC, to provide the asymmetric α-arylation of ester compounds in high ee.
An enantioselective, intermolecular α-arylation of ester enolates to form tertiary stereocenters
Huang, Zhiyan,Liu, Zheng,Zhou, Jianrong
supporting information; experimental part, p. 15882 - 15885 (2011/11/13)
In transition-metal catalyzed, asymmetric α-arylation of carbonyl compounds, formation of tertiary centers with high enantioselectivity is a longstanding problem, due to easy enolization of the monoarylation products. Herein, we report such examples using a palladium catalyst supported by a new, (R)-H8-BINOL-derived monophosphine. Silyl ketene acetals, together with a weakly basic activator, were used as equivalents of ester anions, and they reacted smoothly with aryl triflates in excellent enantiomeric excess (ee). The usefulness of the reaction was demonstrated in a gram-scale synthesis of (S)-Naproxen in 92% ee.
Practical and robust method for regio- and stereoselective preparation of (E)-ketene tert-butyl TMS acetals and β-ketoester-derived tert-butyl (1Z,3E)-1,3-bis(TMS)dienol ethers
Okabayashi, Tomohito,Iida, Akira,Takai, Kenta,Nawate, Yuuya,Misaki, Tomonori,Tanabe, Yoo
, p. 8142 - 8145 (2008/02/12)
(Chemical Equation Presented) We developed an efficient, practical, robust method for the regio- and stereoselective preparation of (E)-ketene trimethylsilyl acetals (KSAs) derived from tert-butyl esters 1. The reaction was performed under convenient reac
Tris(pentafluorophenyl)boron as an Efficient, Air Stable, and Water Tolerant Lewis Acid Catalyst
Ishihara, Kazuaki,Hanaki, Naoyuki,Funahashi, Miyuki,Miyata, Mayumi,Yamamoto, Hisashi
, p. 1721 - 1730 (2007/10/02)
Tris(pentafluorophenyl)boron is an efficient, air stable, and water tolerant Lewis acid catalyst for the aldol-type and Michael reactions of silyl enol ethers with carbonyl compounds or other electrophiles (trimethyl orthoformate, dimethal acetal, and chloromethyl methyl ether), the allylation reaction of allylsilanes with aldehydes, and the Diels-Alder reaction of dienes with α,β-unsaturated-aldehydes.A solution of formaldehyde in water is applicable as an electrophile.Also, the aldol-type reaction of ketene silyl acetals with aromatic or aliphatic imines is successfully carried out using the same catalyst.
Acyclic Stereoselection. 7. Stereoselective Synthesis of 2-Alkyl-3-hydroxy Carbonyl Compounds by Aldol Condensation
Heathcock, Clayton H.,Buse, Charles T.,Kleschick, William A.,Pirrung, Michael C.,Sohn, John E.,Lampe, John
, p. 1066 - 1081 (2007/10/02)
The stereochemistry of the aldol condensation of preformed lithium enolates of a variety of ethyl ketones and propionic acid derivatives with aldehydes has been investigated.It is found that certain compounds give completely or nearly completely one diastereomeric enolate and that the stereostructure of the resulting aldol is correlated with the stereostructure of the enolate from which is formed.The observed stereochemistry may be understood in terms of an ordered transition state in which both oxygens are oriented in more or less the same direction.It is shown that the observed stereochemistry is kinetically controlled.In many cases, the initial aldol adduct equilibrates to furnish predominantly a threo isomer.The rate of equilibration varies widely, ranging from very fast at -60 deg C with the propiophenone-benzaldehyde adduct to slow at 25 deg C for the ethyl tert-butyl ketone-benzaldehyde adduct.The equilibration behavior of lithium ketolates is compared with that of zinc ketolates, and some differences are noted.A method for achieving erythro-threo equilibration via a chloral hemiacetal is presented.A new reagent is introduced (trimethylsilyloxy ketone 36) which may be used to stereoselectively homologate an aldehyde to an erythro α-methyl-β-hydroxy acid.As an application of the use of stereoselective aldol condensations in synthesis, (+/-)-ephedrine (48) has been synthesized from benzaldehyde in 71 percent overall yield.
