Acetate substitution

Norman, R. Taylor, Electrophilic Substitution in Benzenoid Compounds, Elsevier, Amsterdam (1963) 

Taylor, Enzymes in Organic Synthesis, Ciba Foundation Symposium 111, Pitman, London (1985), P 71 

See page 991, Section 1, for addition to the double bond and page 231, Section 5, for oxidation with allylic transposition. 

Mucor plumbeus Rhizopus arrhizus various fungal strains 

Review Comprehensive Organic Synthesis, Eds. B. M. Trost and I. Fleming, Pergamon, Oxford (1991), 7, Part 2.3, p 151 

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Halogen exchange with KF is not successful ia acetic acid (10). Hydrogen bonding of the acid hydrogen with the fluoride ion was postulated to cause acetate substitution for the haUde however, the products of dissolved KF ia acetic acid are potassium acetate and potassium bifluoride (11). Thus KF acts as a base rather than as a fluorinating agent ia acetic acid. 

In 1982, the Schaap group demonstrated that chemiluminescence can be induced by the addition of a base to dioxetanes bearing a phenolic substituent [11]. Herein, the same group presents a method utilizing aryl esterase to catalyze the cleavage of a naphthyl acetate-substituted dioxetane in aqueous buffer at ambient... 

Figure 7.19 Several ligands and gadolinium(III) complexes used in MRI imaging. (A) DTPA ligand (B) [Gd(DTPA)(H20)]2, Magnevist (C) MS-264-L, ethylene-bridge-substituted DTPA (D) BOPTA, acetate-substituted DTPA (E) [Gd(B0PTA)(H20)]2, MultiHance (F) AngioMARK . (Adapted with permission from Chart 1 of Caravan, P. Ellison, J. J. McMurry, T. J. Lauffer, R. B. Chem. Rev., 1999, 99(9), 2293-2352. Copyright 1999, American Chemical Society.)...

Sewald and Wendisch (170) applied the Feringa system to the conjugate addition of diethylzinc to nitroolefins. Optimal selectivities were found for the acetal-substituted nitroethylene (234) providing adduct 235 in 86% ee and quantitative conversion, Eq. 136. 

Gore and co-workers developed a convenient experimental procedure for the conversion of a-phosphate-substituted allene 103 to the preferentially formed E-config-ured 1,3-pentadiene 105 (Eq. 14.13) [46, 47, 51]. In a similar manner, Vermeer and co-workers converted a-acetate-substituted allenes 106 into the corresponding 1,3-dienes 107 in moderate to good yields by simple treatment with organozinc chlorides in the presence of Pd(0) catalyst (Eq. 14.14) [52]. 

Cyclohexyl halides may undergo elimination or substitution reactions. They are usually more prone to elimination, but the acetate anion MeCC>2 is not particularly basic, and nucleophiles are particularly nucleophilic in the polar aprotic solvent DMF. More cyclohexyl acetate (substitution) than cyclohexene (elimination) is likely to form. 

TABLE 18. Alkoxy- and acetal-substituted aryUithiums Li—R by halogen/metal permutation between bromo- or iodoarenes and butyHithium... 

The ROMP of alcohol, ketone, halogen, and acetate substituted cyclooctenes with a ruthenium olefin metathesis catalyst has been reported (31). 

Keywords methanethiol, IV-,5-acetal, substitution, gas-solid reaction... 

A combined experimental and computational approach has been undertaken to identify the origin of syn/anti diastereoselectivity in two types of crotylation reactions of aldehydes and ketones (i) multi-component crotylations of simple aldehydes/ketones and (ii) acetal substitution reactions of aldehyde dimethyl acetals with E- and Z-configured crotyltrimethylsilane.175 The stereochemical outcome is nearly identical in the two reactions, and the computational results suggest that this is due to near identical mechanisms an SN1 process involving attack of O-methyl-substituted carboxenium ions by crotylsilane. 

The Sn reactions of cyclohexanone acetals substituted at C(2) with sulfur, iodine, or chlorine are thought to occur when the nucleophile attacks the oxocarbenium ion intermediate with the substituent on C(2) in an axial conformation.104 The most stereospecific reactions (i.e. >92% trans), were when the substituent at C(2) was sulfur. This mechanism (Scheme 26) is supported by HF/6-31G calculations that show the oxocarbenium ion (66) with the sulfur at C(2) in the axial position to be the most stable, and by the high yield of the trans-isomer (67) in the products. 

Agarans are typically low in sulfate ester substitution, but those from numerous sources are rich in methyl ether or pyruvate acetal substitution in addition, glycosyl substitution (galactosyl, 4-O-methyl-L-galactosyl and/or xylo-... 

Strain 1200 and 1268 expressed identical LPS with the difference that strain 1200 had acetates substituting HepIII, whereas strain 1268 LPS has glycine at the same position. 

Figure 4.9 Carbonylation of methyl acetate to acetic anhydride. The right-hand-side cycle is the same as in 4.1 and 4.2. The big cycle on the left is similar to the organic cycle of 4.2, where acetic acid and methyl acetate substitute for water and methanol. The small inner cycle on the left is the dominant product-forming pathway.

The main interest in the reaction with unsaturated carbonyl compounds lies in the synthesis of heterocycles, mainly pyridines. Simple pyridines can be obtained starting with an alkyl aminocrotonate and acrolein73, an acetal-substituted enol ether74 or benzoylacrylonitriles75 (equation 52). Pyrrolinones are obtained by SnCl4-catalysed action of 3-ethoxycarbonylacrylonitriles on enaminoester75 (equation 53). 

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