Rearrangement of allylic alcohols

Redox Rearrangement of Allylic Alcohols to Chiral Aldehydes... 

Rearrangement of allylic alcohols. RuClj in combination with NaOH is a useful catalyst for isomerization of allylic alcohols of the type RCIIOHClI=CH2 to saturated ketones, RCOCH2CH3. In the isomerization of a chiral allylic alcohol such as I, the product is optically active. The 1,3-hydrogen transfer is 37% stereoselective. 

Rearrangement of allylic alcohols to aldehydes.1 Primary allylic alcohols can isomerize to aldehydes on treatment with LEDA in ethylenediamine (EDA) at 95-130° or with lithium 3-aminopropylamide (6, 476). 

Claisen rearrangement of aUylic alcohols to ethyl dienoates. Claisen rearrangement of allylic alcohols with an orthoacetate is known to provide 2-carbon homologated y,8-unsaturated esters (6, 607-608). Reaction with the phenylsulfinylorthoacetate 1 is accompanied by an in situ sulfoxide elimination to provide 2-carbon homologated dienoate esters (equation I). This novel reagent was used to convert the... 

The oxidative rearrangement of allylic alcohols to a -unsaturated kelmies or alddiydes is one of the most widely used synthetic reactions in this group, and forms part of a 1,3-carbonyl tran sition sequence. Scheme 7 shows this reaction and the related conversion of the allylic alcdiol to an a,p-epoxy carbonyl compound. Chromate reagents induce some allylic alcohol substrates to undergo a directed qmxidation of the alkene without rearrangement, but this reaction is beyond the scope of the present discussion. 

In the acid-catalyzed ortho ester Claisen rearrangement of allylic alcohol (303) with trimethyl orthobutyrate, diastereomers (304), (305) and (306) were isolated in a ratio of 63 30 7 (Scheme 53). The 3,3-sigmatropic rearrangement occuned with a high degree of stereofacial selectivity from the p-face of the allylic alcohol (a >13 1 for Ht). In contrast, Qaisen rearrangement of the enol ether (307) at 135-140 C (PhH, sealed tube) provid the desired -dicarbonyl compound (308) as a single diastereomer at... 

Wang, B. M., Song, Z. L., Pan, C. A., Tu, Y. Q., Chen, W. M. Halogen cation induced stereoselective semipinacol-type rearrangement of allylic alcohols. A highly efficient approach to a-quatemary 3-haloketo compounds. Synlett 2003,1497-1499. 

In the synthesis of steroid precursors containing a C 5 ethylated side chain, the rearrangement of allylic alcohol 5 via Eschenmoser rearrangement involves both relative and internal asymmetric induction yielding all possible diastereomers459-460. 

Both the allyl vinyl ether, as well as the ortho ester rearrangement of allylic alcohol 14, give rise to the formation of a single diastereomer 16 or 18633. New bond formation occurs from the side opposite to the isopropyl group. 

Unsaturated esters 32 are obtained by ortho ester Claisen Cope rearrangement of allylic alcohols 30 as nearly 1 1 EjZ mixtures because of the relatively equal steric bulk of the methyl and the acetic acid ester group in the Cope rearrangement of 31. Due to the mild reaction conditions required for the first Claisen step, intermediate 31 can be isolated 224 -1159. 

A feature of the acrolein-allyl alcohol reaction is the small but measurable production of propyl alcohol. This product could arise by rearrangement of allyl alcohol to propionaldehyde followed by hydrogen exchange of propionaldehyde with either ethyl alcohol or allyl alcohol. 

Preparation of monomeric vinyl alcohol from acetals, by rearrangement of allyl alcohols (to 1-propene-l-ols) and polymerization thereof [240,241]. 

Finally, the Tu group reported a novel transfer fluorination/semipinacol rearrangement of allylic alcohols that generated enantioenriched fluorinated products containing a chiral quaternary carbon center (Scheme 13.4) [12]. Quinine was identified as the optimal Cinchona alkaloid for this transformation. While the majority of substrates examined contained cyclohexenes, resembling the one shown in Scheme 13.4, substrates containing a cycloheptene and an acyclic allylic alcohol were also suitable for this transformation. 

The [3,3]-sigmatropic rearrangement of allylic alcohols after condensation with ethyl 3,3-diethoxyacrylate leads to regiospecific syntheses of substituted allyl malonates in good yields (Scheme... 

Another example of orthoester rearrangement for the construction of a quaternary center is given in the enantioselective synthesis of (-t)-valerane 148 [34]. In this synthesis, ii-(-)-carvone 149 is used as starting material. Rearrangement of allylic alcohol 150 afforded ester 151. Diazoketone cyclization is then followed by a ring enlargement affording the bicyclo[4.4.0]decane system (Scheme 6.22). 

---