Secondary alcohol moiety

Matsuo T, Nishioka T, Hirano M, Suzuki Y, Tsushima K, Itaya N, Yoshioka H (1980) Recent topics in the chemistry of synthetic pyrethroids containing certain secondary alcohol moieties. Pestic Sci 11 202-218... 

The resolution of anti-3-methyl-l,4-pentanediol (60) proceeds via rapid Novozym 435 (CALB) catalyzed monoacylation with vinyl acetate in TBME under dry conditions followed by a slower enantioselective acylation of the secondary alcohol moiety (Scheme 4.23) [82]. Similarly, diasteromerically pure threo- and erythro-3-methylalkan-2-ols of type 61 and 62, respectively, have been successfully acylated with 2/(-preference ( E > 100 to >1000) using vinyl acetate, propionate or butyrate... 

Studies in the laboratory of M. Shibasaki toward the total synthesis of garsubellin A led to the stereocontrolled synthesis of the 18-ep/-tricyclic core of the natural product/ During the final stages of the synthetic sequence, the tetrahydrofuran ring was installed using a Wacker-type process. The reaction conditions insured that the acetonide protecting group was first removed and the Cl 8 secondary alcohol moiety served as the internal nucleophile to form the tricyclic product. 

The endoethano- or endoethenotetrahydrothebaine derivatives 115 with either a tertiary or secondary alcohol moiety were reported to undergo fragmentation under acidic conditions to give 14-alkenyl derivatives 116 (Scheme 37)11 [98-102]. 

These polynucleating macrocyclic ligands sometimes have a mind of their own and do not form the desired tetranuclear species. Thus, under certain conditions, ligands of type L H4 or L H4, which contain short-chain alcohol backbones, do not deprotonate at the secondary alcohol moiety. They form polymeric species with Cu(II) halides or azides, probably because of the small macrocyclic ring size (304). Somewhat similar effects were alluded to earlier in regard to the tetraphenolic Schiff-base macrocycles (263), and we have had related experiences with open-chain analogues (305). 

Scheme 29 Chemoselective oxidation of a secondary alcohol moiety with Ru catalysts. " ...

Chemoselective oxidation of a secondary alcohol moiety can be also performed with ruthenium catalysts with phenylindenyl Hgand. The selective oxidation of 1-phenylethanol to acetophenone from a mixture of phenylethanol isomers, without oxidizing the other isomer, can then be achieved (Scheme 29). In general, only the secondary alcohol moieties are oxidized and the catalyst can be used for the chemical separation of isomers or specific oxidation of highly functionalized molecules. The OKR of unactivated racemic alcohols with dioxygen of air as the hydrogen acceptor was effectively performed at room temperature with [(aqua)Ru(salen)] com-... 

Furthermore, they integrated two distinct enantioselective chiral Zn(II) catalyses, HDA and diethylzinc addition reactions, in one pot in a sequential manner (Scheme 4.27). The desired product was obtained with both dihydropyranone and secondary alcohol moieties from terephthalaldehyde in excellent selectivity (> 93% yield, 97.4% ee) by using 10mol% of the combined catalyst (87)/Zn(II)/(92). 

Synthetic analogues have been prepared as exemplified in Scheme 14 [95]. A first Wittig-Homer olefination of aldehyde 107, followed by acidic treatment, generates cyclohexenone 108. Chemo- and stereoselective reduction of the latter with 9-BBN followed by sy -selective epoxidation of the allylic alcohol (lateral hydroxyl group control) by w-chloroperbenzoic acid gives 109. Selective tosylation of its secondary alcohol moiety (steric hindrance makes the tosylation of the tertiary alcoholic moiety difficult) and subsequent deprotonation of the tertiary alcohol with NaH provide an alcoholate that undergoes an intramolecular displacement reaction. 

Scheme 61 Asymmetrization of cyclic me o-diols containing two secondary alcohol moieties.

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