Base-catalyzed, acylation

Base-catalyzed acyl transfer reaction that converts a-acyloxyketones to (3-diketones. 

Section A.5). Indeed, three enantiomeric pairs of 2-oxazolidinones have been commercially available since 1991. Enantiomerically pure 4-phenyl-2-oxazolidinone has likewise been prepared from / -aminobenzeneethanol (phenylglycinol)64. Base-catalyzed acylation of the enantiomerically pure 2-oxazolidinones with an appropriate acyl chloride gives the desired 3-acyl-2-oxazolidinones 3, 6 and 9 which have been used extensively in highly diastereoselective reactions of various types such as alkylations, aldol reactions (see Section D.l.3.4.2.4), hydrox-ylations (see Section D.4.1), aminations (see Section D.7.1) and Diels-Alder reactions (see Section D. 1.6.1.6) alkylation giving products with induced chirality in the a-position. 

It has been suggested155 that a base-catalyzed, acyl-transfer reaction occurs in certain reactions involving 3, 5 -di-0-aroyI derivatives of... 

Bac2 Base-catalyzed, acyl-oxygen cleavage, bimolecular... 

Although aspartimide formation can occur during base-catalyzed acylation in Boc-based chemistry, the reaction is more pronounced during Fmoc removal with piperidine.The reaction, shown in Scheme 6, is sequence dependent, but aspartimide formation can be up to 0.3% per N-terminal deprotection cycle when the required peptide contains -Asp-Gly-. When the resultant peptide is cleaved from the support the aspartimide ring may remain intact, but can also open to form the P-branched peptide. 

Acylation of 3,4,7,8-tetramethylglycoluril by the method of Sun and Harrison [34] leads to the monoacyl derivatives, which can be further selectively acylated with lithium diisopropylamide (LDA) and acyl chlorides. The resulting symmetrical or asymmetrical diacyl compounds undergo a base-catalyzed acyl transfer reaction. Consequently, the glycoluril acts as a temporary template that facilitates a condensation between acyl units. The absence of O-acylation products is explained by chelation of the lithium by the intermediate enolate. 

A new synthesis for 2-substituted Isoquinolines starts with o-toluo-nltrlle. Base catalyzed acylation followed by ketalizatlon gives the key intermediate. Reduction of the amine followed by acid cycllzation and dehydrogenation (I2) gives the heterocycle. 

Carbodiimide method, a procedure for peptide bond formation using carbodi-imides, R-N=C=N-R, such as dicyclohexyl carbodiimide (DCC), diisopropyl carbodiimide (DIC) and water-soluble carbodi-imides. The carbodiimide reacts in a one-pot procedure with the carboxylate anion of the carboxy component to form a highly reactive O-acylisourea intermediate. The former reacts immediately with the amino function of the amino component to yield the desired peptide derivative and the urea byproduct. Indeed, a more complex mechanism must be taken into consideration. Unwanted side reactions are racemization via the oxazolone mechanism and formation of the unreactive N-acylurea by base-catalyzed acyl migration from the isourea oxygen to nitrogen. The side reactions can be diminished by preparing the O-acylisourea at 0 °C... 

Base-catalyzed acyl substitution reactions also occur in three steps. 

MECHANISM OF NUCLEOPHILIC ACYL SUBSTITUTION Acid-Catalyzed Acyl Substitution Reactions Base-Catalyzed Acyl Substitution Reactions Relative Reactivity of Acyl Derivatives... 

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