Oxidative deallylation

Glycosylation between glucosaminyl donor 147 and inositol acceptor 148 followed by Ir-catalyzed deallylation provided the pseudodisaccharide core 149 (Scheme 13.22). It was coupled to the phosphoglycerolipid derivative 150 with the use of 17/-tetrazolc as mild acidic promoter and then oxidized with iBuOOH at low temperature to avoid epoxidation of the unsaturated lipid. The phosphoglycerolipidated pseudodisaccharide then underwent TBS deprotection to afford the desired 4 -alcohol 151. 

In dioxane, when X = O or RN, the reaction proceeds smoothly. However, when a methyl group is introduced into the olefmic moiety, the reaction is suppressed. On the other hand, in DMAC the introduction of a methyl group to the olefmic moiety does not affect the catalytic activity, though when X = O or RN, a deallylation reaction proceeds to disturb the cyclization reaction. In DMAC, oxidative addition of the allyl-X group to the ruthenium active species would occur, most likely due to the coordination of a more electron-donating amide solvent. Thus, the two reports are mutually supportive. 

The catalytic activity of these oxo-Fe complexes has also been investigated in detail. For example, the first one isolated, [TMC-Fe =0] , displayed catalytic activity in the transfer of orygen towards triphenylphosphine (PhaP), yielding the corresponding phosphine oxide Ph3P=0. Other interesting iron-based catalytic processes are the oxidative M-deallylation of... 

In 2008, Nicolaou andLi reported a synthesis of diversonol (932) (Scheme 13.14) (635). The synthesis involved the nucleophilic addition of a lithiated cyclohexene species derived from bromide 938 with the allyl-protected aldehyde 939, followed by oxidation, desilylation, deallylation, and spontaneous xanthone-ring closure of the intermediate phenol (not shown). As in the Brdse synthesis, the enol moiety is oxidized and the C-ring ketone reduced with NaBH4 to generate diversonol (932), which was obtained in eight steps from cyclohexenone 937. 

Bailey and Liebeskind independently discovered the anionic cycUzation shown in Scheme 1 [1, 2] that leads to indoUnes and, by subsequent oxidation, to indoles. Both methods are virtually identical, involving bromine-lithium exchange followed by quenching of the aryllithium species with an electrophile (equations 1 and 4). The Af-allylindole can be deallylated with palladium (equation 2) [3], and the indohne is easily oxidized to the corresponding indole (equation 3). A selection of indoles prepared this way by Liebeskind and Zhang is shown (1-6) [2], The yields are overall for the two steps. These workers also employed chloranil (f-BuOMe, rt) to oxidize indohnes to indoles. An excellent review by Bailey and Mealy is available [4]. Bailey s related indoline synthesis via arynic cycUzation is presented in the later chapter on NucleophiUc CycUzation of Arynes (Chapter 65). 

This year has seen several approaches to the core of the zaragozic acids/squalestatins from carbohydrate starting materials. D-Mannose was converted to the glycal 117, elaborated to precursor 118 by a-selective dioxirane oxidation and Cl epoxide ring opening by allyl alcohol, deallylation, oxidation and Grignard addition. Desilylation of 118 with concomitant intramolecular acetalation afforded the core analogue 119 (Schone 30). ... 

N,N-diallylmelamine , vasodilator. Rat, dog, man. Extensively metabolized. N-oxidation (triazine ring, reversible reaction) to form active metabolite, then deallylation and N-reduction (rat) direct deallylation (M) (all species) hydroxylation of allyl group N-methylation (triazine ring) then deallylation UP in urine. Species difference - man does not produce active metabolite, (N-hydroxy triazine derivative). 

Kondo and Mitsudo are the pioneers of transition-metal-catalyzed retro-allylation [7]. They described this phenomenon as deallylation and fi-allyl elimination . Ruthenium-catalyzed reaction of tertiary homoallylic alcohols proceeds in the presence of allyl acetate under an atmosphere of carbon monoxide in tetrahydro-furan (THF) at a relatively high temperature of 180 C to afford the corresponding ketones (Scheme 5.3). Although the exact roles of allyl acetate and carbon monoxide are not clear, they propose a mechanism involving oxidative addition of the... 

P-aminoacyliron complexes in moderate yield and good diastereomeric excess. Deallylation of these products using palladium(O) catalysis gives the corresponding homochiral secondary amines. On oxidative demetalation with bromine or -bromo-succinimide, concomitant cycli2ation occurs to afford P-lactams (Scheme 4-48). ... 

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