Benzoyloxy group

Delphinine contains one hydroxyl, one methylimino and four methoxyl groups, which with the acetoxy and benzoyloxy groups accounts for all the oxygen atoms of the alkaloid. 

The allylic position of olefins is subject to attack by free radicals with the consequent formation of stable allylic free radicals. This fact is utilized in many substitution reactions at the allylic position (cf. Chapter 6, Section III). The procedure given here employs f-butyl perbenzoate, which reacts with cuprous ion to liberate /-butoxy radical, the chain reaction initiator. The outcome of the reaction, which has general applicability, is the introduction of a benzoyloxy group in the allylic position. 

However, in the case of a compound containing the electron withdrawing benzoyl group, p-elimination of the benzoyloxy group occurred and an enone was obtained in the presence of hydrogen and boric acid (Scheme 4.143).541... 

A rearrangement reaction involving migration of a benzoyloxy group explains... 

Diels-Alder reactions.1 1,3-Dienes react with 1 to form adducts that undergo ready loss of the benzoyloxy group to provide nitrobenzenes. 

Hoppe and Gonschorrek also reported the interesting formation of an enyne structure [137]. Deprotonation of allenyl carbamates 242 bearing a benzoyloxy group caused a 1,4-elimination of lithium benzoate, furnishing 1-alkynyl carbamates 243 in moderate to good yield (Scheme 8.63). 

Absolute and relative rates of ETR of tert-butyl perbenzoates with dimethyl sulfide at various temperatures (T = 80, 90, 100 and 110°C) were obtained. Hammett correlations at each temperature were also studied (Table 7). The Hammett slopes are positive and the reactions are better correlated with a rather than with cr. This indicates that a negative charge resides on the benzoyloxy group without conjugation with the phenyl... 

The thermolysis of benzoyl peroxide in thiophene gives a complex mixture, with the phenylation products accounting for only 3%. Considerable amounts of 2,2 -bithienyl and products containing the benzoyloxy group are formed. The suggested mechanism is shown in Scheme 59, according to which the benzoyloxy radicals are efficiently trapped before fragmentation to C02 and phenyl radicals. 

Similar reaction of l-O-acetyl-2,3,5-tri-0-benzoyl-/ -D-ribose (36) on a small scale and in a cooled reactor gave the product of direct substitution, namely, l-0-acetyl-2,3,5-tri-0-benzoyl-4-bromo-/ -D-ribose (37), but, on a larger scale, or without cooling, an equilibrated mixture of the ribo and the l-lyxo bromides (37 and 38) was produced (see Scheme 8). The former, with the benzoyloxy group at C-3 and the bromine atom m-related, was readily... 

Radical substitution may also proceed through the cation radical stage. The monograph by Nonhebel and Walton (1974) discusses the introduction of the benzoyloxy group into the aromatic ring. Thus, the interaction of benzoyl peroxide with the benzene deriva-... 

In the case of tri-O-benzyl-D-glucal, entirely different chemistry is observed, with the initially formed cation 102 abstracting a hydride ion from the 0-6 benzyl group to give the 3-deoxy species 103. Intramolecular addition to C-2 affords 104 and the initially cleaved benzoyloxy group adds to C-l to give the unusual bicyclic 105 in 45% yield (Scheme 12).120... 

Indeed, the insight into the intricate stereochemical details of ensuing reactions of the pyranoid enolone ester bromide 3 - the pyranoid enolone ester 14, de facto, is an actinospectoside derivative, 16 a structural element of the spectinomycin as well as uscharidine-type cardiac glycosides (except for the terminal benzoyloxy group) - eventually led to practical synthetic strategies for their acquisition. 

The stereochemistry of acetoxy group addition to tram-4, 4 -dimethoxystil-bene 52 is analogous. However, the recent finding 101 that the analogous reaction, anodic addition of two benzoyloxy groups across a double bond, produces the same mixture of products from both cis- and frans-stilbene (stereochemistry the same as in equation (31) ), would seem to make the adsorption requirement unnecessary. The stereoselectivity is then explained on the basis of formation of the thermodynamically most stable acetoxonium ion in a stepwise oxidation mechanism1011. 

The last alkaloid, compound L, named knightolamine (12), is closely related to (11) except for the lack of a carbonyl group in an acetyl ester and the presence of a benzoyloxy-group (1740 cm ) the parent ion (M+ 367 C HzsNOJ is cleaved to an ion of m/z 246 and a benzoyloxyl radical. The fragment of m/z 94 usually appears in the mass spectrum of those tropanes8 that have a hydroxy-group in the pyrrolidine moiety. 

Oxidation of pyrrolizines. Reactioa of /-butyl perbenzoate with bicyclic pyrrole derivatives such as 1 results in introduction of the benzoyloxy group at C in 40-45% yield. Lead tetraacetate, selenium dioxide, DDQ, and NBS are not useful for oxidation of 1. ... 

The final disconnection c, projected to give -lactams by amidyl radical cychsations, was investigated by Clark et al. [91,92], Treatment of 0-benzoylhydroxamic acid derivatives 96 with BusSnH and AIBN using slow addition furnished the azetidinones 98, via 4-exo cyclisation of the corresponding amidyl radicals 97, accompanied by the straight reduction product and a benzoyloxy group migration product 99 (Scheme 21). 

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