91328-33-5Relevant academic research and scientific papers
63. Enantioselective Formation of Bicyclic Lactones by Rhodium-Catalyzed Intramolecular CH-Insertion Reactions
Mueller, Paul,Polleux, Philippe
, p. 645 - 654 (2007/10/02)
The decomposition of cyclohexyl diazoacetate (5a) in the presence of the chiral 4> catalyst leads to a 3:1 cis/trans mixture of bicyclic lactone 6a with an enantiomeric excess of 95-97percent (cis) and 90percent (trans).The conformationally rigid tert-butyl derivatives 5b and 5c afford, in the presence of the same catalyst, 6b and 6c, respectively, via insertion into the equatorial C-H bonds exclusively, with ee's of ca. 95percent.A remarkable degree of induction (92-95percent) results in the lactone 6g upon decomposition of 1-isopropyl-2-methylpropyl diazoacetate (5g).The diazoacetates derived from 1-methylcyclohexanol, cyclopentanol and 1-methylcyclopentanol (5d-f) afford under similar conditions insertion products with higher diastereoselectivity, but significantly lower enantioselectivity.Other dirhodium catalysts are less efficient.
Cobalt(II) Chloride Catalyzed Acylation of Alcohols with Acetic Anhydride: Scope and Mechanism
Iqbal, Javed,Srivastava, Rajiv Ranjan
, p. 2001 - 2007 (2007/10/02)
Cobalt(II) chloride catalyzes the acetylation of a variety of alcohols with acetic anhydride in excellent yield.Primary hydroxyl groups can be selectively acylated in the presence of secondary and tertiary ones while the secondary hydroxyl groups can be preferentially acetylated in the presence of tertiary ones.Tertiary alcohols have been found to give ketones, acetoacetates, olefins, and diketene in addition to the acetate.The β-hydroxy esters and ketones can be acylated under these conditions without any elimination, and this reaction has been compared with 4-(dimethylamino)pyridine (DMAP)-mediated acylations where elimination of the resulting β-acetoxy carbonyl compound is observed.A detailed investigation of the acylation of tertiary alcohols has revealed that these reactions proceed via a tertiary alkoxy radical and ketene.A mechanism for these acylations is proposed by invoking an electron-transfer process.
Transacetoacetylation with tert-Butyl Acetoacetate: Synthetic Apllications
Witzeman, J. Stewart,Nottingham, W. Dell
, p. 1713 - 1718 (2007/10/02)
Reaction of various nucleophiles with tert-butyl acetoacetate (t-BAA, 1a) is shown to be a convenient method for the preparation of a wide variety of acetoacetic acid derivatives.This material can be used to prepare acetoacetates and acetoacetamides from a wide variety of alcohols and amines.Reaction of 1a with an unhindered primary amine such as n-heptylamine under standard conditions gives unwanted byproducts due to the formation of the enamines 24 and 25.Formation of these byproducts can be minimized by dilution and/or altering the mode of addition.
Acetoacetylation with 2,2,6-Trimethyl-4H-1,3-dioxin-4-one: A Convenient Alternative to Diketene.
Clemens, Robert J.,Hyatt, John A.
, p. 2431 - 2435 (2007/10/02)
The diketene/acetone adduct, 2,2,6-trimethyl-4H-1,3-dioxin-4-one, efficiently acetoacetylates aliphatic and aromatic alcohols, amines, and thiols.These acetoacetylation reactions are fast and stoichiometric, require no catalysis, and give only volatile byproducts.
Formation of Cyclic Carbonates in the Reaction of 1,2-Ditertiary Diols with Acetic Anhydride and 4-(Dimethylamino)pyridine
Bhushan, Vidya,Chakraborty, Thushar K.,Chandrasekaran, Srinivasan
, p. 3974 - 3978 (2007/10/02)
The reaction of 1,2-ditertiary diol 1a with acetic anhydride and 4-(dimethylamino)pyridine (DMAP) at high concentrations in the absence of solvent has been found to give rise to cyclic carbonate 2a.The reaction has been generalized with a few other 1,2-ditertiary diols (1b-d).Based on the different products isolated in these reactions, apart from a small amount of normal acetylation products, various mechanisms have been proposed and examined.Tertiary alcohols have been found to give monoacetoacetates in addition to the acetates, under the same conditions.Detailedinvestigations have prompted us to suggest the intermediacy of ketene and diketene in these reactions.
