Acyl fluorides catalytic

Silyl enolates react with acyl cation equivalents to give the C- and/or O-acylated products (Equation (90)).333 Fluoride-catalyzed reaction using acyl fluorides is valuable for O-acylation of silyl enolates derived from aldehydes and ketones.334 CuCl also promotes the 0-acylation with acyl chlorides.335 The CuCl-promoted reaction of ester silyl enolates results in exclusive (7-acylation. Combined use of BiCfl and Znl2 (or Nal) effects catalytic (7-acylation of ketone silyl enolates with acyl chlorides. 

Insertion of HFA into the C—F bonds of perfluorinated dicarboxylic acyl fluorides has been achieved thermally under the catalytic influence of potassium fluoride (70). 

The enantioselective protonation of silyl enol ethers, such as (12.39), by a catalyst has been achieved using 2 mol% of the proton source (12.40). The acidity of (12.40) is enhanced by coordination to a Lewis acid. The silyloxy group is activated by fluoride ion and up to 99% ee in the asymmetric protonation of a-aryl substituted cyclic silyl enol ethers such as (12.39) has been obtained using a Lewis acidic BINAP. / F complex.In a similar vein, silyl enol ethers of tetralones and indanones undergo asymmetric protonation with moderate to good ee using catalytic quantities of hydrogen fluoride salts of cinchona alkaloids in the presence of acyl fluorides and ethanol, which act as a stoichiometric source of HE 28... 

Triflates of aluminum, gallium and boron, which are readily available by the reaction of the corresponding chlorides with triflic acid, are effective Fnedel-Crafis catalysis for alkylation and acylation of aromatic compounds [119, 120] Thus alkylation of toluene with various alkyl halides m the presence of these catalysts proceeds rapidly at room temperature 111 methylene chloride or ni-tromethane Favorable properties of the triflates in comparison with the correspond mg fluorides or chlorides are considerably decreased volatility and higher catalytic activity [120]... 

Bulkier C -trifluoromethylated a-amino acids do not react or result in substantial racemi-zation (epimerization) of the nonfluorinated amino acids in the sequence. 106,113 114 Therefore, alternative pathways have been developed. The in situ deprotection of /V-Teoc-( Tfm)Xaa derivatives, in the presence of a catalytic amount of fluoride ions and Fmoc-Xaa-F, allows for the N-acylation of the (aTfm)Xaa with acceptable yields (Scheme 6). 111,113 Very recently, the multicomponent Ugi reaction has also been explored with the aim of incorporating (aTfm)Xaa at the C-terminal position of peptides. 114 ... 

Af-Trimethylsilyl enamines undergo TV-acylation on treatment with acid chlorides (replacement of the trimethylsilyl group) to give the amide and starting ketone on hydrolysis. However, in the presence of potassium fluoride and a catalytic amount of crown ether, C-acylation occurs to give the a-acylimine in high yield196 (Scheme 85). 

A more efficient route to 2-(benzoyloxy)vinyl ether (15) involves (0 °C, THF) conversion of the chiral alkoxy aldehyde 14 to its silyl enol followed by 0-acylation with benzoyl fluoride and a catalytic amount of TBAF (2 mol %) to form a separable mixture of the Z-vinyl ether (81%) and E-vinyl ethers (6%) (eq 8). 

A special one-pot deprotection-transacylation method involves coupling of activated Fmoc amino acids with Aloc-protected amino acid esters.The Aloc-deprotection proceeds with palladium/phenylsilane in the presence of the acylating species. Using Fmoc-Phe-F the synthesis of the sterically demanding dipeptide Fmoc-Phe-(Me)Aib-OMe was accomplished in a yield of 65% A similar one-pot approach to the acylation of the even more difficult hindered and weakly nucleophilic a-trifluoromethyl amino acid esters involves the intermediate A-Teoc protection. Thus treatment of ( )-Teoc-a-(a-CF3)Leu-OMe with Fmoc-Gly-F and a catalytic amount of tetraethylammonium fluoride in acetonitrile at 50 °C for 1-2 weeks gave ( )-Fmoc-Gly-(a-CF3)Leu-OMe (77%... 

Irreversible inhibitors are effectively esteratic site inhibitors which, like true substrates, react with the hydroxyl group of serine at the catalytic active site. Such inhibitors, sometimes referred to as acid-transferring inhibitors, include the organophosphates, the organo-sulfonates, and the carbamates. All form acyl-enzyme complexes which, unlike substrate-enzyme intermediates, are relatively stable to hydrolysis. Indeed, the phosphorylated enzyme intermediates have half-lives from a few hours to several days (A12), whereas the sulfonated or carbamylated enzyme complexes have much shorter half-lives—several minutes to a few hours. Several strong lines of direct evidence point to the formation of an acyl complex—the isolation of phosphorylated serine from hydrolysates of horse cholinesterase (J2), complex formation and carbamylation (02), and the sulfonation of butyrylcholinesterase by methanesulfonyl fluoride in the presence of tubocurarine and eserine (P6). 

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