Acylal formation

Interestingly, acylal formation has been accomplished with acetic anhydride [37] on K 10 clay (75-98%) as well as deacylation [38]. 

In the presence of a large excess of olefin, most of the HCo(CO)4 is quickly converted to the acyl compound and none is available for acyl cleavage to the final products hence, under these conditions aldehyde yield is very low and a 1 1 ratio of absorbed CO HCo(CO)4 is approached. On the other hand, in the absence of a large excess of olefin, the rate of acyl formation is slower, and sufficient HCo(CO)4 is available to cleave the... 

The symmetry of transformation (107) is identical to that of the alkyl car-bonyl-to-acyl conversion, (5), and therefore the difference in the propensities of these insertions to occur must relate to differences in the orbital energetics of the two processes. Since the metal-nitrosyl jr-interaction is a dominant feature of the electronic structure in NO+ complexes, and since it will be weakened by the formation of a nitroso species, one can expect (107) to be correspondingly less favorable than acyl formation in (5). If reaction (107) does occur, however, one can readily envisage tautomerism of the nitroso ligand to an oxime. The reactive nature of the oxime may then create difficulties in the identification and isolation of organonitrogen products, and indeed, this may have obscured general observation of transformation (107) in the past. 

The formation of 1,1-diacetates 5 from aldehydes 4 and Ac20 dates back to early systematic studies by Knoevenagel [9]. A representative example is given with the preparation of compound 5a in Scheme 8.1. Several groups have since then developed improved protocols for acylal formation [10]. It was realized that these gem-diacetates such as compound 5b are perfect substrates for palladium-catalyzed... 

Scheme 8.1 FeCI3-catalyzed acylal formation as reported in 1914 (product 5a) and 2001 (product 5b).

With the Fe-Pd complex lb which contains a less electron donating -Si(OSiMe3)3 siloxane ligand, no acyl formation was observed but instead the p-carbene complex 9 was formed quantitatively upon bubbling of CO for 5 min. through a solution of lb (Eq. 7). 

Sc(OTf)3 also catalyzes acetalization reactions [47a,b], acylal formation [47c], /9-selective glycosilation reactions with thioglycosides [48], and acylation reactions of alcohols [49]. Guanidium formation reactions of carbodiimide with benzylamine [50], intermolecular stereoselective radical additions to A/-enoyloxazolidinones [51], and rearrangement of... 

Bulky phosphine ligands inhibit expansion of the coordination sphere. Oxidative addition to CpM(CO)L was followed by acyl formation for M = Co and Rh oxidative addition may also be followed by a decarbonylation, as shown for the rhodium complex, RhfPMejPhlsCP ... 

The following rhenium cyclic compound does not undergo acyl formation with CO whereas ring expansion with CO occurs with the corresponding manganese derivative ... 

Kostanecki acylation. Formation of chro-mones or coumarines by acylation of o-hydroxyaryl ketones with aliphatic acid anhydrides followed by cyclization. 

The cells of D. discoideum harbor the machinery for post-translational protein modifications such as phosphorylation, acylation, formation of glycosyl phosphatidyl-inositol anchors, and, in particular, O-hnked and N-hnked glycosylation [90, 91]. 

Side reactions such as double-bond migration and others are observed, similar to hydroformylation. Mechanistically, hydrocarboxylation is related to hydroformylation up until the metal acyl formation stage13. The presence of an acidic compound shifts the reaction towards formation of carboxylic acid derivatives and suppresses reductive elimination which forms aldehydes. The mechanism of the final steps is unclear13. 

Acylation. Formation of bicycUc lactams related to the Pauson-Khand reaction is realized from 5,6-alkadienal hydtazones by heating with Mo(CO)6 and DMSO in CH2CI2 at 100°. With thiocarbonyl compounds the reaction leads to thiolactones. ... 

Olah, G. A., Mathew, T., Famia, M., and Prakash, G. K. S. 1999. Nafion-H catalysed intramolecular Friedel-Crafts acylation formation of cyclic ketones and related heterocycles. Synlett 1067-1068. 

A study using Rh(OAc)(cod)/phosphine as the catalyst (Scheme 1-39) showed the highest rate for dppf among the many phosphines tested. Its selectivity to saturated linear pentanal is better than that of PPhj but inferior to that of dppe. The rate enhancement generally shown by diphosphine complexes 92 is attributed to it ds-chelation effeet, which imparts a neighboring group effect via a cis disposition of the carbonyl to the Callyl. This proximity effect facilitates subsequent acyl formation whereas the trans configuration 93 would be unfavorable [250]. Recently, the idea of diphosphine-enrichment has been extended to asymmetric hydroformyla-... 

The acyl formation reaction is suggested to proceed via initial attack at the carbyne carbon, but evidence is not conclusive. Reaction of the analogous Cp complexes with cyclohexene sulfide provides exclusively the dithiocarboxylate derivatives. Presumably the second sulfur addition is considerably more rapid than for the Tp complexes due to lowered steric crowding around the molybdenum... 

Friedel-Crafts acylation Formation of an acylbenzene by substitution of an acylium ion on an aromatic ring. (p. 775)... 

Effect of acylation. Formation of lysinoalanine from lysine re-quires the participation of an e-amino group of a lysine side chain. Therefore, it was expected that protection of amino groups by acylation (acetylation, succinylation, etc.), would reduce ly-sinoalanine formation under alkaline conditions, if the protective group (s) survived the treatment. Results in Tables strikingly demonstrate that acetylation of wheat gluten prevents lysinoala-nine formation. 

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