Homoallylic alcohols, via

Allylboron compounds have proven to be an exceedingly useful class of allylmetal reagents for the stereoselective synthesis of homoallylic alcohols via reactions with carbonyl compounds, especially aldehydes1. The reactions of allylboron compounds and aldehydes proceed by way of cyclic transition states with predictable transmission of olefinic stereochemistry to anti (from L-alkene precursors) or syn (from Z-alkene precursors) relationships about the newly formed carbon-carbon bond. This stereochemical feature, classified as simple diastereoselection, is general for Type I allylorganometallicslb. 

DMI is the solvent of choice for the conversion of allylic iodides to homoallylic alcohols via an allyltin dihaloiodide (equation I).3... 

Interestingly, the use of optically active alcohol 51 in this protocol leads, after cleavage of the benzylic ether in the initial adduct 52, to the enantiomerically enriched homoallylic alcohol 26. This approach appears to be the first asymmetric preparation of homoallylic alcohols via open-chain acetal derivatives (Scheme 13.19). 

Table 15 Preparation of homoallyl alcohols via three-component coupling. Reproduced with permission from the Royal Society of Chemistry...

J-menthol. In addition, this complex also catalyzes the intermolectdar hetero-ene reaction between activated enophdes and olefins to give homoallylic alcohols via a stepwise process (Scheme 10.27) [53],... 

The formation of chiral secondary homoallylic alcohols via the enantioselective addition of allylic nucleophiles to aldehydes is an important tool in organic synthesis. An efficient way to achieve this transformation is to use allylic organometallic reagents in the presence of chiral Lewis acid catalysts. The most widely studied catalysts in the area... 

Hoffmann, R. W., Herold, T. Enantioselective synthesis of homoallyl alcohols via chiral allylboronic esters. Angew. Chem. Int. Ed. 1978,17, 768-769. 

Formaldehyde can be coupled to an alkene in the presence of an acid to give a diol (152) or a 1,3-dioxane derivative (154) in what is known as the Prins reaction. l Allylic alcohols such as 153 can also be produced in this reaction. Camphene (155) reacted with formaldehyde and acid to give a 1 1 mixture of allylic alcohol 156 and the acetate 157, in 94% yield. Scandium tiiflate has been used to prepare tetrahydropyran-4-ol derivatives from aldehydes and homoallylic alcohols via a Prins-type cyclization. 3... 

Trans-1,2-dichlorocyclohexane (16) was electrolyzed under the same conditions as 12 to afford as main product 49% 17 (equation 9). The inductive effect of the two chlorine atoms deactivates C ) and C e) so strongly that the oxidation is directed mainly to C(4) and C 5j. Also, the extent of cleavage of the C—Cl bond is decreased compared to the results of 12. The high selectivity and the decreased formation of side products can provide here a synthetically useful route from olefins to homoallylic alcohols via protection of the double bond, anodic oxidation, hydrolysis and deprotection. 

Knorr 1932, The application of Gilman and McGlumphy s method for the preparation of allylic Grignard reagents does not look very attractive for industrial use only two years after its publication, the first patent for the preparation of homoallylic alcohols via the one-step Barbier reaction was applied for [42]. 

Shintani R, Takatsu K, Hayashi T (2008) Rhodiimi-catalyzed kinetic resolution of tertiary homoallyl alcohols via stereoselective carbon — carbon bond cleavage. Org Lett... 

Silicon is also more electropositive (Pauling eleetronegativity index 1.8) than carbon (2.4), and the silicon-carbon bond is polarized Si -C . Tetravalent silicon, a weak Lewis acid, is thus essentially attacked by anions (F, etc.) to form hyper-valent silicon derivatives. This phenomenon is used for the sterie control of reactions that proceed in the coordination sphere of silicon. For instance, fluorides and catecholate anions, among others, catalyze the stereoselective reaction between an allylsilane and an aldehyde leading to the corresponding homoallylic alcohols via an anionic intermediate of pentavalent silicon ... 

Scheme 3 Stereoselective synthesis of homoallyl alcohols via Ni-catalyzed C-O bond activation...

Rhodium-catalyzed retro-allylation represents an interesting tool for enan-tioselective carbon-carbon bond cleavage. Shintani and Hayashi developed rhodium-catalyzed kinetic resolution of tertiary homoallylic alcohols via retro-allylation (Scheme 5.40) [28]. The bidentate BINAP series show high selectivity... 

R. W. Herold, T. 1981. stereoselective synthesis of alcohols VII. optically active homoallyl alcohols via addition of the chiral boronates to aldehydes. Chem. Ber. 114 375-383. 

Three closely related reports have appeared on the stereoselective functionalization of allylic and homoallylic alcohols via iodo-carbonates (38) (Scheme 25). In an extension of earlier work (6,171), carboxylation-halogenation of allylic and homoallylic alcohols has been used as a route to triols (39). Homoallylic t-butyl carbonates (40) have also been found to undergo halogenation to afford (38b) in acetonitrile (to capture the t-butyl cation) subsequent conversions lead to diols (41) or triol monoethers (42). The iodination of homoallylic carbamates (43) also leads to (38b), and hence to diols (41). In all of these methods, the carbonates (38b) from homoallylic alcohols are formed with a preferred, 3-syn arrangement of the oxygen atoms. 

Bongini A, Cardillo G, Orena M, Porzi G, Sandri S. Regio-and stereocontrolled synthesis of epoxy alcohols and triols from aUylic and homoallylic alcohols via iodocarbonates. J. Org. Chem. 1982 47 4626 33. 

---