Lewis Base Catalyzed Enantioselective Allylic Hydroxylation of Morita–Baylis–Hillman Carbonates with Water
摘要:
A Lewis base catalyzed allylic hydroxylation of Morita-Baylis-Hillman (MBH) carbonates has been developed. Various chiral MBH alcohols can be synthesized in high yields (up to 99%) and excellent enantioselectivities (up to 94% ee). This is the first report using water as a nucleophile in asymmetric organocatalysis. The nucleophilic role of water has been verified using O-18-labeling experiments.
Correlation between p<i>K</i><sub>a</sub> and Reactivity of Quinuclidine-Based Catalysts in the Baylis−Hillman Reaction: Discovery of Quinuclidine as Optimum Catalyst Leading to Substantial Enhancement of Scope
作者:Varinder K. Aggarwal、Ingo Emme、Sarah Y. Fulford
DOI:10.1021/jo026671s
日期:2003.2.1
powerful combination of quinuclidine with methanol was tested with a host of aldehydes and Michaelacceptors. Not only were the reactions more efficient and faster than previously reported, but now new substrates that were previously unreactive could be employed. Notable examples include the use of acetylenic aldehydes and the employment of vinyl sulfones, acrylamides, delta-lactones, and even alpha
Regioselective S<sub>N</sub>2' Mitsunobu reaction of Morita–Baylis–Hillman alcohols: A facile and stereoselective synthesis of α-alkylidene-β-hydrazino acid derivatives
作者:Silong Xu、Jian Shang、Junjie Zhang、Yuhai Tang
DOI:10.3762/bjoc.10.98
日期:——
regioselective SN2' Mitsunobu reaction between Morita-Baylis-Hillman (MBH) alcohols, azodicarboxylates, and triphenylphosphine is developed, which provides an easy access to alpha-alkylidene-beta-hydrazino acid derivatives in high yields and good stereoselectivity. This reaction represents the first direct transformation of MBH alcohols into hydrazines.
Development of catalysts for the Baylis–Hillman reaction: the application of tetramethylguanidine and attempts to use a supported analogue
作者:Nicholas E. Leadbeater、Cornelia van der Pol
DOI:10.1039/b106267k
日期:2001.11.1
We show here that tetramethylguanidine (TMG) is a useful catalyst for the BaylisâHillman reaction of aldehydes with methyl acrylate, showing good activity with a range of aldehyde substrates and, unlike many other catalysts or catalyst mixtures, it can be used to good effect with simple aliphatic aldehydes. We show that the activity of the catalyst is decreased when the reaction is run using solvents rather than solvent-free but, in the case where a solvent is necessary, dichloromethane offers the best results. Attempts to use supported or derivatised TMG complexes as catalysts for the reaction have been unsuccessful suggesting that the presence of an amine hydrogen is key to the activity of TMG. Attempts to use stabilised aliphatic phosphines as catalysts for the reaction have proven partly successful, with only modest yields of product being obtained with 2-(dicyclohexylphosphino)biphenyl and 2-(di-tert-butylphosphino)biphenyl. The Verkade superbase, P(MeNCH2CH2)3N,
proved inactive as a catalyst, an adduct with the acrylate being the only product formed.
Superior amine catalysts for the Baylis–Hillman reaction: the use of DBU and its implications†
作者:Varinder K. Aggarwal、Andrea Mereu
DOI:10.1039/a907754e
日期:——
DBU, which is normally regarded as a hindered and non-nucleophilic base, is in fact the optimum catalyst for the BaylisâHillman reaction, providing adducts at much faster rates than using DABCO or 3HQD; the scope of the BaylisâHillman reaction is enhanced using this catalyst and implications of this finding are discussed.
One-Pot Preparation of 1-Acyl-1-methoxycarbonyloxiranes and 1-Acyl-1-cyanooxiranes from Methyl 3-Hydroxy-2-methylenealkanoates or 3-Aryl-3-hydroxy-2-methylenepropanenitriles
作者:André Foucaud、Eliane le Rouillé
DOI:10.1055/s-1990-27016
日期:——
The reaction of sodium hypochlorite with methyl 3-hydroxy-2methylenealkanoates or 3-aryl-3-hydroxy-2-methylenepropanenitriles, dispersed on silica gel, in acetonitrile leads to oxidation of the alcohol function and epoxidation of the methylene group to give 2,2-disubstituted oxiranes in good yield.