Alkenes allyl alcohol derivatives

The allylic acyloxylation of alkenes, the Kharasch-Sosnovsky reaction, Eq. 81, would be an effective route to nonracemic allylic alcohol derivatives, if efficient, enantioselective catalysts were available. The reaction is mediated by a variety of copper salts, and as such, has been the target of considerable research in an attempt to render the process enantioselective. The original reaction conditions described by Kharasch require high temperatures when CuBr is used as the catalyst (93). However, the use of CuOTf (PhH)0 5 allows the reaction to proceed at temperatures as low as -20°C. Unfortunately, long reaction times are endemic in these processes and the use of excess alkene (2-100 equiv) is conventional. Most yields reported in this field are based on the oxidant. 

One of the classical ways to perform diastereoselective 1,3-dipolar cycloaddition is by the addition of a 1,3-dipole to an allyl alcohol derivative (65, 107-120). Very recently, a short review article was devoted to this area (13). Among the most commonly applied acyclic allyl alcohol derivatives are alkenes 73-75 (Scheme 12.25). These alkenes have been used in reactions with nitrones. 

Numerous chiral cyclic allyl alcohol derivatives have been used as the chiral alkene part in 1,3-dipolar cycloadditions. In general, the more rigid conformational... 

Blechert carried out a tandem reaction of enynes in the presence of olefins instead of ethylene (Scheme 21). Treatment of cyclopentenol derivative 58a with Ic in the presence of an alkene affords 59a. The five-membered ring in estrone 58b is cleaved by Ic to give 59 and an alkene part is introduced on the six-membered C ring. However, cycloalkenyl amine derivative 60 is treated in a similar manner in the presence of an allyl alcohol derivative to give pyrrolidine derivative 61, and in this case, an alkene part is introduced on the diene moiety. Presumably, ruthenium carbene complex XVI reacts with an alkyne part to produce the pyrrolidine ring with a regioselectivity opposite to the other cases. 

As expected, with tertiary allylic alcohol derivatives, the selectivity for the formation of the corresponding trisubstituted alkenes is significantly reduced. Eschenmoser rearrangement of alcohol (281), for example, led in 92% yield to a 7.1 1 ratio of ( )- to (Z)-amides (282) and (283) (Scheme... 

Recently, Ni-catalyzed allylic substitutions of simple alkenes for the formation of 1,4-dienes 174 have been described by Jamison and Matsubara. Allylic alcohol derivatives 172, bearing a variety of leaving groups, can be coupled with a wide range of simple alkenes 173 including gaseous ethylene and propylene. The key for the reaction was the use of the appropriate nickel-phosphine complex and a stoichiometric amount of a silyl triflate. Reactions of 1-alkyl-substituted alkenes... 

The direct ruthenium catalysed allylation with allylic alcohol derivatives of various aromatic compounds and heterocycles such as furans and thiophenes was performed by Nishibayashi with cationic thiolate-bridged diruthenium(III, II) catalysts. The reaction is consistent with an electrophilic aromatic substitution by the electrophilically activated allyl moiety [68]. Allylation also takes place with the alkene metathesis Grubbs catalyst [69]. More importantly using (phosphine-sulfonate)ruthenium(II) catalyst Bmneau et al. have recently shown that allyl alcohols are activated generating an allyl-ruthenium(IV) intermediate leading to C3-allylation of indole with high regioselectivity in favour of the branched allyl derivative [(Eq. 84)] [167]. 

The l,5-hexadien-3-ol derivatives 792 and 794 are cycli2ed to form the cyclo-pentadiene derivatives 793 and 795 by insertion of an alkene into -allylpalla-dium formed from allylic alcohols in the presence of trifluoroacetic acid (lO mol%) in AcOH[490],... 

The cyclohexadiene derivative 130 was obtained by the co-cyclization of DMAD with strained alkenes such as norbornene catalyzed by 75[63], However, the linear 2 1 adduct 131 of an alkene and DMAD was obtained selectively using bis(maleic anhydride)(norbornene)palladium (124)[64] as a cat-alyst[65], A similar reaction of allyl alcohol with DMAD is catalyzed by the catalyst 123 to give the linear adducts 132 and 133[66], Reaction of a vinyl ether with DMAD gives the cyclopentene derivatives 134 and 135 as 2 I adducts, and a cyclooctadiene derivative, although the selectivity is not high[67]. 

Potential precursors to stereoselective INOC and ISOC reactions (e.g., 195 and 196, respectively) have been prepared via stereoselective conjugate additions of several allylic alcohols (e.g., 194,X = 0) and an allylic thiol (e.g., 194,X = S) to a chiral (E)-nitro alkene (e. g., 193) that was derived from (P)-2,3-isopropylidene... 

A mild, Fe(CO)5-catalyzed isomerization of this type was reported by Gree and coworkers [173]. Allylic alcohols having mono-, di-, trisubstituted alkene are readily converted into their corresponding ketones, whereas polyunsaturated derivatives do not rearrange (Scheme 54). 

Wilkinson s catalyst has also been utilized for the hydroboration of other alkenes. Sulfone derivatives of allyl alcohol can be hydroborated with HBcat and subsequently oxidized to give the secondary rather than primary alcohol. This reactivity proves to be independent of substituents on the sulfur atom.36 Similarly, thioalkenes undergo anti-Markovnikoff addition to afford a-thioboronate esters.37 The benefits of metal-catalyzed reactions come to the fore in the hydroboration of bromoalkenes (higher yields, shorter reaction times), although the benefits were less clear for the corresponding chloroalkenes (Table 3).38,39 Dienes can be hydroborated using both rhodium and palladium catalysts [Pd(PPh3)4] reacts readily with 1,3-dienes, but cyclic dienes are more active towards [Rh4(CO)i2].40... 

Reaction of the allyltitaniums with D20 and NCS proceeds with excellent regioselectiv-ity, and thus a new one-pot method for converting ally] alcohol derivatives to 1-alkenes having D and Cl at the allylic position is opened up (Eq. 9.26) [46]. 

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