Homo-allylic alcohols oxidation

Reaction of 66 with Ipc2BOMe followed by BF3 Et20 provides the allylborane 15. Allylation of aldehydes with 15 and subsequent alkaline hydroperoxide oxidation yields syn P-methoxy homo-allylic alcohol 69 in very high de and ee (Scheme 25.8). 

The preparation of the requisite y-keto-p-toluenesulfonate rac-35 as homo-Favorskii precursor commenced with commercially available 2,5-dihy-droanisole (36) that was protected and epoxidized to acetal rac-31 (Scheme 11). Regioselective opening of the epoxide with p-chlorophenylse-lenide followed by sequential oxidation to the selenoxide and thermal elimination generated an allylic alcohol that was protected to give pivaloate rac-38. 

A general method for the preparation of 3,7-substituted allyl alcohols with (Z)-configuration has been developed with alkyllithium. The regioselectivity of the reactions of alkynyllithium and oxiranes ° ° and the effects of the solvent and (Me2N)3PO ° have been investigated with regard to the formation of homo-propargyllic alcohols. The stereochemistry of the process has been studied in the reactions of as- and fra 5-neopentylallyllithium with cyclohexene oxide and fra s-2,3-butene oxide. 

A series of homo-allylic steroidic alcohols were oxidized with N-methyl morpholine N-oxide (NMO) in the presence of tetrapropylammonium perrhutenate (TPAP) (Eq. 70, see Ch. 9, p. 358).The mechanism probably implies the preliminary oxidation of the alcohol. A labile silyl enol ether is preserved under the conditions specified. 

The structure of ( —) 2P-acetoxy-1 la-hydroxyverrucosane (544) was established as follows (Scheme 65). Jones oxidation of (544) gave a five-membered ketone (551). Acid treatment of the latter resulted in homoallylic ring expansion to homo-allylic ketoalcohol (552) which was converted via the tosylhydrazone into (548) identical with the homoallylic alcohol prepared from (547) via (545) (Scheme 64). That the 11-hydroxyl group was a was inferred from the remarkable downfield shifts exhibited by the C-10 and the C-12 methyl groups of the five-membered ketone (551) and the small solvent shift exhibited by the C-10 methyl group (553) and its homoallylic ring expanded product. 

Multi-component reactions open a direct access to poly-functional derivatives/ For instance, reactions of unsaturated substrates and aldehydes in the presence of EtaSiH opened a rapid access to allyllic, homo-allylic or co-unsatu-rated alcohols, and NHC-Ni complexes were recently reported to be efficient catalysts for such oxidative coupling. Mori and co-workers described the first example of such condensation in 2001. They showed that an in situ generated IPr/Ni 1 1 complex led to the stereoselective formation of (Z)-homoal-lylic silyl alcohols [eqn (10.33)], while classical Ni -PPhj catalyst produced only (Ej-coupling products. Of note, IPr/Ni 1 2 and IMes/Ni 1 2 were less efficient in this reaction. These first results were extended to silylated dienes. Interestingly, it was shown that a mixed complex [(IPr)Ni(PPh3)] stereoselectively produced (Z)-allylsilanes while [Ni(PPh3)4] led only to (Ej-isomeric products. 

Suginome, H. and Wang, J.B., Intramolecular P,y-addition of allylic alkoxyl radicals. A new general synthesis of a-iodoepoxides by photolysis of allylic alcohol hypoiodites in the presence of mer-cury(II) oxide, iodine and pyridine in benzene, /. Chem. Soc., Chem. Commun., 1629,1990. Suginome, H., Isayama, S., Maeda, N., Furusaki, A., and Katayama, C., Photo-induced transformations. 57. The formation of bridged oxabicycHc compounds by intramolecular radical addition of oxyl radicals generated from some A-homo-4a-cholesten-3-ol hypoiodites, /. Chem. Soc., Perkin Trans. 1, 2963,1981. 

The oxidahon of olefins with aqueous hydrogen peroxide in methanol can produce several products, by different reachon paths double bond epoxidation, allylic H-abstraction, epoxide solvolysis, alcohol and glycol oxidation (Scheme 18.6). Normally, oxide catalysts of Group IV-Vl metals are poorly selechve, because of their acidic properhes, the inhibition they are subject to in aqueous media and homo-lytic side reachons with hydrogen peroxide. The only excephon concerns the epoxidahon of a,(3-unsaturated alcohols and acids, which are able to bind on the... 

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