Furyl alcohols, oxidation

Alcohols are practically inert towards DIB at room temperature and react very slowly at elevated temperature, unless they possess special features. Thus, oxidation due to the presence of furan ring occurred in a series of furyl alcohols which with DIB alone or better in combination with magnesium perchlorate (in a molar ratio 1 2) were converted into pyran-3(6//)-ones [129]. 

Since the enolization is not restricted to the 2 and 3 positions, a number of products are formed that undergo subsequent aldol condensations and the Cannizzaro oxidation. They are all 2-hydroxy-3-methyl, 3,4-dimethyl-2-hydroxy, 3,5-dimethyl-2-hydroxy, and 3-ethyl-2-hydroxy-2-cyclopenten-l-ones sugar acids acetic acid hydroxyacetone three isomeric hydroxy-2-butanones y-butyrolactone and such furan derivatives as furyl alcohol, 5-methyl-2-furyl alcohol, and 2,5-dimethyl-4-hydroxy-3(2H)-furanone. They are food flavoring agents. 

The oxidation of 2-furyl alcohols 33 using (-t-)-DIPT as a chiral source provides (l )-furyl alcohols of >95% ee and pyranone when 0.6 equivalents of TBHP are used [73,74]. This stereochemistry is consistent with the empirical rules for kinetic resolution of secondary allyUc alcohols (Scheme 11). Both the optically... 

In general it is aldehydes of aromatic hydrocarbons and of heterocycles that can be subjected to this reaction, named after its discoverer the Cannizzaro reaction but there a similar oxidation-reduction, brought about by an enzyme, plays an important part in biological events in the cell. In the laboratory the Cannizzaro reaction serves for preparation of both acids and alcohols, each normally in 50% yield. As example, the preparation of 2-furoic acid and fur-furyl alcohol from 2-furaldehyde is here recorded.499... 

Furyl alcohol 2-Furylcarbinol a-Furylcarbinol. See Furfuryl alcohol 2-Furyl methanal. See Furfural (2-Furyl) methanol. See Furfuryl alcohol Fused boric acid. See Boron oxide... 

Fremy s salt will oxidize benzylic and furyl alcohols under... 

Furfural, which is prepared from corncobs, is an important solvent in synthetic rubber manufacturing, and it is reduced to fur-furyl alcohol, which is used to make polymer resins. Furfural can also be oxidized to 2-furoic acid. 

Two equivalents of pyridinium chlorochromate oxidize 5-bromo-2-furyl alcohols to the 4-hydroxy-butenolides (49) in 60—75% yield (three examples, R = simple alkyl). 

The Achmatowicz reaction is based on the foregoing oxidative cleavage of the fiiran ring in furyl alcohols 49, whose oxidation is preferentially performed with tert-butyl hydroperoxide or MCPBA. The primarily formed l-hydroxy-2,5-dicarbonyl compounds 50 immediately cyclize to the corresponding pyranones 51 by intramolecular hemiacetal... 

Chlorination. Methanesulfonyl chloride can effect the direct chlorination of various substrates. The most notable of these reactions is the selective chlorination of the C-6 primary hydroxy group of carbohydrates (eq 2). Under these conditions, 2-furyl alcohol (eq 3) and guanine V-oxide (eq 4) can also be chlorinated directly. 

With N-hydroxysuccinimide as mild oxidant and RuCl(cyclopentadienyl)(cy-clooctadiene) as catalyst precursor, in the presence of tris(o-furyl)phosphine and n-butylammonium bromide, a wide range of homopropargylic alcohols were transformed into five-membered y-butyrolactones via a related cydoisomeriza-tion-oxidation reaction [21]. 

Homopropargylic alcohols as well as propargylic epoxides and pentynols readily form cyclic ruthenium alkoxycarbenes upon intramolecular nucleophilic addition of the OH group to the electrophilic a-carbon of ruthenium-vinylidene species. Their oxidation in the presence of N-hydroxysuccinimide leads to the formation of penta-lactones. The best catalytic system reported until now for this transformation of but-3-ynols is based on RuCl(C5H5)(cod), tris(2-furyl)phosphine, NaHCOs as a base, in the presence of nBu4NBr or nBu4NPp6, and N-hydroxysuccinimide as the oxidant in DMF-water at 95 °C (Scheme 8.11) [22]. 

The first total synthesis of the clerodane alkaloid solidago alcohol was achieved in the laboratory of H.-S. Liu, using a highly diastereoselective DIels-Alder cycloaddition as the key step. The installation of the 3-furyl side chain required the conversion of the bicyclic primary alkyl bromide to the corresponding aldehyde. This was accomplished by the modified Kornblum oxidation, which employed silver tetrafluoroborate to activate the substrate. 

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