Furylcarbinols

The solution is then placed in a continuous extraction apparatus (Org. Syn. 3, 88) and the 2-furylcarbinol is extracted with 1500-2000 cc. of ether (Note 4). The extraction is complete after six to seven hours. 

When extraction is complete the ether solution of 2-furylcarbinol is distilled until the temperature of the liquid (not the vapor) reaches 95°. Then the residue is distilled under diminished pressure. Some ether and water come over first and the temperature then rises rapidly to the boiling point of 2-furylcarbinol. The yield of 2-furylcarbinol boiling at 75-77°/iS mm. is 310-325 g. (61-63 psr cent of the theoretical amount) (Note 5). 

Carbon tetrachloride may be used for the extraction of the 2-furylcarbinol. This requires altering the extraction apparatus to remove the solvent from the bottom of the extraction bottle. Some difficulties are met in working with carbon tetrachloride, due to the liberation of acid which causes the 2-furylcarbinol to change into the water-insoluble form. The yields of both 2-furancarboxylic acid and 2-furylcarbinol are much lower when carbon tetrachloride is used as a solvent. 

The 2-furylcarbinol thus obtained is entirely soluble in water and has only a slight yellow tinge. If it is to be stored, about 0.5 to I per cent of its weight of urea should be added as a stabilizer. 

Furylcarbinol has been prepared by the reduction of furfural with sodium amalgam but the Cannizzaro reaction is the better practical method of preparation. 

Chemical Designations - Synonyms 2-Furancarbinol, Furfuralcohol, alpha-Furylcarbinol, 2-Furylcarbinol, 2-Hydroxymethylfuran Chemical Formula CjHjOj. 

Addition of carbon nucleophiles to furfural tosylhydrazone provides 5-substituted 2E,4E-pentadienyls in good yields <00TL2667>. The ab initio calculations at the RHF/3-21G level have been utilized to study the origins of diastereoselectivity of the vinylogous Mannich reaction of 2-methylfuran with pyrrolinium ion . A simple procedure for isomerization of 2-furylcarbinols to cyclopentenones under neutral condition was reported and a new mechanism was proposed <00H(52)185>. 

The reversal of the well-known transformation of sugars into pyrans has been detailed as a method for assembling simple monosaccharides from simple furans (71T1973). A compound of the 2-furylcarbinol type was converted by the Br2/MeOH procedure into a mixture of the cis and trans isomers of the corresponding 2,5-dimethoxy-2,5-dihydrofuran derivative (129). Mild acid hydrolysis of (129) resulted in cleavage of the acetal bonds with formation of the dicarbonyl compound (130) which underwent immediate cyclization to 2,3-dideoxy-DL-alk-2-enopyranos-4-ulose (131 Scheme 29). 

Pyridinium chlorochromate in dichloromethane reacts with furans to give a range of products, but they are all formed by 1,4-electrophilic attack of chlorochromate on the furan ring the fate of the resultant intermediate (57) by heterolytic cleavage of the Cr—O bond depends on the substituents at the a-positions of the substrate. 2,5-Dialkylfurans yield a, /8-unsaturated-y-dicarbonyl compounds, 5-methyl-2-furylcarbinols yield pyran derivatives, and 5-bromo-2-furylcarbinols yield 5-hydroxyfuran-2(5//)-ones (Scheme 25) (80T661). 

Methoxy-2-furylcarbinols (367) were converted into a 3 1 mixture of 4-ylidene-butenolides (369) and 4-oxo-2-enoic acid methyl esters (370) by zinc chloride catalysis. The carbonium ion (368) is the key intermediate, the stability of which made the conversion very fast, providing high yields (Scheme 99) (80T3071). 

Furylcarbinol (CoU. Vol. i, 270) A product of high purity is obtained in excellent yields by hydrogenation of furfural at about 175° and so-too atm. pressure with copper chromite catalyst. Calingaert and Edgar, Ind. Eng. Chem. 26, 878 (1934). 

A somewhat similar problem is revealed by the acid-catalyzed ring opening of oxetans (104). These are formed by photochemical [2 + 2] additions, and with boron fluoride or aluminium chloride they supply 3-furylcarbinols (105) mixed, however, with the isomeric 2-furylcarbinols (106). With toluene-sulfonic acid only the expected 3-furylcarbinol results, but this is changed into the 2-isomer when treated with one of the Lewis acids. The rearrangement is believed to be effected by dissociation into furan and a carbenium ion... 

Honda T (1997) Oxidative ring transformation of 2-furylcarbinols in natural products. In Atta-ur-Rahman (ed) Studies in natural products chemistry, vol. 19. Elsevier Science BV, Amsterdam... 

Subsequent to the Cannizzaro reaction, sufficient sulfuric acid is added to liberate substantially all of the pyromude add and to cause resinification in situ of the 2-furylcarbinol when the mixture is heated. Trickey and Miner, U. S. pat. 1,665,236 [C. A. 22, 1783 (1928)]. 

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