Decalinic allylic alcohol

Allyl W-phenylimidates rearrange upon heating in refluxing decalin at 190 °C to give ,<5-unsat-urated anilides in moderate diastereoselectivitics, probably due to nonstereoselective formation of the ketene /V,0-acetal intermediates, e.g., formation of 1 and 2250. The diastereoselectivities are opposite to those observed in Vleerwein- Eschenmoser rearrangements (cf. p 3406). Products with a syn relationship predominate in the rearrangement of allyl W-phenylimidates derived from. E-allylic alcohols. 

In 2013, Liao reported the first asymmetric total syntheses of the sesquiterpenoid lactones (+)-eudesmadiene-12,6-olide and (+)-fruUanolide, which were based oti an initial dearomatization of 4-bromo-2-methoxyphenol 240 into the corresprMidmg MOB 241 (Fig. 58) [129]. An asymmetric Diels-Alder reaction wifli the chiral furan R)-2A2 furnished the bicyclo[2.2.2]octenone 243 in good yield with high chemo-, regio-, and stereoselectivities. This compound was further transformed in a few steps to reach (+)-eudesmadiene-12,6-olide, whose m-decalin core was elaborated by a high-yielding anionic oxy-Cope rearrangement of the allylic alcohol 244 (Fig. 58) [129]. 

In contrast to (Lewis) acid-catalysed annulations of /3-keto-esters such as (222), which lead to decalins cf. refs. 175,176), mercuric ion-induced cyclization of (222) leads instead to the pyran (223). Further examples of the ability of a carbon-tin bond to provide a specific nucleophilic site in TiCU-catalysed cyclizations of allylic alcohols have been reported, together with a full account of the use of an imino group to initiate polyene cyclizations annulations of imines that carry a chiral substituent result in moderate chiral inductions. 

As can be seen from Table VI, secondary aliphatic, allylic, and benzylic alcohols are all quantitatively converted into the corresponding carbonyl derivatives. It is interesting to note that no epimeriza-tion of menthone takes place under these conditions (Entry 3). Furthermore, rather hindered decaline derivatives (Entry 5) are also smoothly oxidized. 

The allyl boronate 101, prepared by treatment of the cis-decalin diol 100 with trisallylborane, underwent allylation with dihydrocinnamaldehyde to afford the corresponding homoallylic alcohols favoring the R-enantiomer, which was the major enantiomer predicted based on transition-state calculations. Although the level of enantioselectivity realized with 100 is low, further refinements of the computational parameters should lead to the discovery of more efficient chiral ligands.39... 

Silylmethyl radical cyclizations are a related class of reactions in which the heterocycle serves a temporary purpose to direct the introduction of a methyl or hydroxymethyl group adjacent to the hydroxy group. Starting from the optically active allylic decalin alcohol, reaction with bromomethyl(chloro)dimethylsilane gives the a-bromosilyl ether. Treatment with tributyltin hydride affords the stereoselective cyclization to a five-membered siloxane62. The siloxane ring is converted either to the a.r-dihydroxy compound, or to the ot-methylated derivative63. 

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