Secondary allylic alcohol functionality

In the stereoselective total synthesis of ( )-14-deoxyisoamijiol by G. Majetich et al., the last step was the epimerization of the C2 secondary allylic alcohol functionality. The Mitsunobu reaction resulted only in a poor yield (30%) of the inverted product, so the well-established sulfoxide-sulfenate rearrangement was utilized. The allyic alcohol was first treated with benzenesulfenyl chloride, which afforded the thermodynamically more stable epimeric sulfenate ester via an allylic sulfoxide intermediate. The addition of trimethyl phosphite shifted the equilibrium to the right by consuming the desired epimeric sulfenate ester and produced the natural product. 

With respect to the olefinic substrate, various functional groups are tolerated, e.g. ester, ether, carboxy or cyano groups. Primary and secondary allylic alcohols, e.g. 14, react with concomitant migration of the double bond, to give an enol derivative, which then tautomerizes to the corresponding aldehyde (e.g. 15) or ketone ... 

Unlike 4-19, the Heck reaction is not limited to activated substrates. The substrate can be a simple olefin, or it can contain a variety of functional groups, such as ester, ether,319 carboxyl, phenolic, or cyano groups.320 Primary and secondary allylic alcohols (and even nonallylic unsaturated alcohols321) give aldehydes or ketones that are products of doublebond migration,322 e.g.,... 

Placement of the directing function at the 3-position (66) is also effective but regiochemistry of epoxi-dation is dependent upon the substitution of the hydroxy-bearing carbon. With secondary allylic alcohols the major product is the cyclopentenone with the allenyl epoxide as a minor by-product (equation 36). Tertiaiy alcohols give allenyl epoxides exclusively. ... 

This system found another application—the oxidation of secondary alcohols into ketones in excellent yield. It is worthy of note that the oxidation procedure tolerates other functional groups including iodide, ester, terminal alkyne, aromatic ether, and 1,3-dioxolane. Certain secondary allylic alcohol such as 2-cyclododecen-l-ol (31) produced the corresponding epoxy ketone 32 in one pot, as exemplified in Sch. 17. 

The inhibitor possesses end ether and allylic alcohol functional groups while the antibiotic possesses a phenol and a secondary amide functional group. 

There are other strategies for directly functionalizing ortho positions. Christopher 1. Moody of the University of Nottingham has found J. Org. Chem. 2007, 72,10298) that phenols such as 24 can be coupled with secondary allylic alcohols to give, after Claisen rearrangement, the alkylated product 26. 

The method is not restricted to secondary aryl alcohols and very good results were also obtained for secondary diols [39], a- and S-hydroxyalkylphosphonates [40], 2-hydroxyalkyl sulfones [41], allylic alcohols [42], S-halo alcohols [43], aromatic chlorohydrins [44], functionalized y-hydroxy amides [45], 1,2-diarylethanols [46], and primary amines [47]. Recently, the synthetic potential of this method was expanded by application of an air-stable and recyclable racemization catalyst that is applicable to alcohol DKR at room temperature [48]. The catalyst type is not limited to organometallic ruthenium compounds. Recent report indicates that the in situ racemization of amines with thiyl radicals can also be combined with enzymatic acylation of amines [49]. It is clear that, in the future, other types of catalytic racemization processes will be used together with enzymatic processes. 

Allyl Alcohols. Secondary cyclic allylic alcohols are reduced with the combination of Et3SiH and ethereal LiC104, even in the presence of a tertiary alcohol (Eq. 35) or ketal function.173 Primary allylic alcohols do not undergo deoxygenation under similar conditions.173... 

Several substituted l-oxaspiro[4.5]dec-6-enes have been prepared by employing a mild amberlyst-15-catalyzed Sn2 oxaspirocyclization. As can be seen below, the tertiary <00TL3411> and secondary <00TL3415> allyl alcohols 89 serve as the n-allyl cation precursors and the other hydroxy groups function as nucleophiles. 

Catalytic alcoholysis reactions between secondary silanes and allylic alcohols give allyloxyhydrosilane products, in which Si-H and C=C double bond functionalities are present [Eq. (61)]. 

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