Benzyl alcohol triple

A soln. of FeClg in tetrahydrofuran added to a suspension of NaH in the same solvent, stirred 4 hrs. at room temp, under argon, benzaldehyde in tetrahydrofuran added, stirring continued at room temp., and the product isolated after 24 hrs. -> benzyl alcohol. Y 85%. F. e., also sec. alcohols from ketones, and with FeClg instead of FeClg, s. T. Fujisawa, K. Sugimoto, and H. Ohta, J. Org. Chem. 41, 1667 (1976) also hydrogenation of carhon-carbon double and triple bonds s. Chem. Lett. 1976, 581. 

Boukouvalas and co-workers employed an intramolecular oxycarbonylation of benzyl alcohol 89 in the asymmetric synthesis of (—)-panacene, tetrahydrofuroben-zofuran derivative, which holds the prominent position of being the archetypical member of a family of marine bro-moallenes. ° The synthesis of the panacene building block 89 (Scheme 15.22) starts from the aldehyde 87, which is accessed from commercially available 2-methoxy-6-metyl-benzoic acid. An asymmetric alkynylation of 87 followed by reduction of the triple bond with hydrogen over Lindlar... 

Fluorodehydroxylation of Alcohols. DAST, like several other variants of dialkylaminotrifluorosulfuranes, converts primary, secondary, tertiary, allylic, and benzylic alcohols to monofluorides. The reaction conditions are mild (temperature as low as —78 to 0 °C for reactive substrates), and a variety of functionalities such as acetonides, isolated double/triple bonds, esters, ethers, amides, and unactivated halides are tolerated (eqs 1-3). ... 

Addition of palladium on carbon to this system markedly enhances the reactivity and permits reduction of nonactivated carbon carbon double and triple bonds. One advantage of this system over catalytic hydrogenation is that cycloptopyl groups and benzylic ethers and alcohols are not affected. Yields are generally higher than... 

Catalytic hydrogenation is a standard method for cleaving benzylic ethers. The resulting secondary alcohol constitutes the nucleophilic reaction center in a subsequent Michael addition to the acceptor-substituted triple bond. Compound 5 is obtained quantitatively with a double bond in the trans configuration. 

A Lewis-basic substituent in the alkene can also promote addition of a Grignard reagent to a double or triple bond. Allyl, benzyl, and t-butyl Grignard reagents add readily to allylic and homoallylic alcohols and alkynols (equation 49). A magnesium alkoxide, formed initially, apparently assists intramolecularly in the addition. There appear to be multiple mechanistic pathways, with different stereochemistries. OR and NR2 groups also activate addition. 

Titanium acetylides react with 3-benzyl-tetrahydro-l,3-oxazines and 1,3-oxazolidines to give the corresponding / -aminoacetylenes in modest to good yield.296 Vinyl Ti(iv) species prepared by the alkylation of vinylcarbene complexes with BTCl react with aldehydes to give allylic alcohols. Reaction with terminal alkynes produces conjugated dienes, in which a vinyl group regioselectively bonds to the unsubstituted side of carbon-carbon triple bond.297... 

One of die most popular reactions in organic chemistry is dissolving metal reductions [1-3], Two systems are frequently used - sodium dissolved in ammonia with alcohol and lithium dissolved in alkylamines [4]. Although calcium is seldom used, it has been successfully applied to the reduction of a variety of compounds and functional groups [5], including aromatic hydrocarbons, carbon-carbon double and triple bonds, benzyl ethers, allyl ethers, epoxides, esters, aliphatic nitriles, dithianes, als well as thiophenyl and sulfonyl groups. 

In a total synthesis of sterols, van Tamelen et al. [11] developed a new method for selective removal of a benzyl group in an alkyne bearing a non-terminal C-C triple bond. Treatment of polyenyne benzyl ether 9 with 4.4 equiv. calcium in liquid ammonia gives the corresponding alcohol 10 in 92% yield (Scheme 4.2). 

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