Furan diol

Some of the typical conditions of polycondensations used for aliphatic and aromatic monomers are not suitable for furan derivatives, e.g., the melt polycondensation of 2,5-furan dicarboxylic acid chloride with 2,5-b/s(hydroxymethyl) furan at about 80 °C only yields a black insoluble product5. The hydrochloric acid liberated in the reaction is clearly responsible for the charring of the furanic diol which like its simpler homologue furfuryl alcohol, resinifies rapidly in acidic media (see below). 

A. Agarwal, S. Rani, and Y. D. Vankar, Protic acid (HC104 supported on silica gel)-mediated synthesis of 2, 3-unsaturated-O-glucosides and a chiral furan diol from 2,3-glycals, J. Org. Chem., 69 (2004) 6137-6140. 

Treatment of D-glucal with a catalytic amount of Sm(OTf)j or RuQ2(PPh3)3 in the presence of one equivalent of water afforded an optically active furan diol <99CC965>. 

M. Hayashi, H. Kawabata, and K. Yamada, Metal-catalyzed transformation of D-glucal to optically active furan diol, Chem. Commun. (Cambridge), (1999) 965-966. 

B. S. Babu and K. K. Balasubramanian, A facile synthesis of a chiral furan diol from glycals catalyzed by indium trichloride, J. Org. Chem., 65 (2000) 4198-4199. 

When D-glucal is treated with 10 mol% InCl, 3H2O in acetonitrile the chiral furan diol is obtained. n-Galactal also undergoes transformation to the same product (Scheme 8.129) [172]. Indium tribromide and trichloride efficiently catalyze the chemoselective fhioacetalization of carbonyl compounds (Scheme 8.130) [173]. 

A concise sequence was developed for the total synthesis of )-6-q>i-cleistenolide (14EJO8049). It required only five steps in an overall yield of 60% from the commercially available furylallyl alcohol.The aforementioned Achmatowicz reaction took place with the furan diol intermediate to give the dihydropyranone product.The final product was obtained via a sequence of oxidation, reduction, and acetylation. 

Biocatalyzed formation of chiral furane diols Sufficient amount of 5 as an intermediate despite the higher amount of GDH applied via route A, the bottleneck was supposed to be at low activity of GDH towards furan compounds. In fact, in route B when ZI ADH was applied, with glucose dehydrogenase (GlucDH) for cofactor regeneration, this resulted in excellent isolated yields (87%) and enantioselectivity (>99% ee, (5)) [46-49] (Scheme 12.2). 

Biocatalytic formation of chiral furane-diols via route A. 40 mL phosphate buffer 50 mmol L-1, pH 8.0, 5% v/v 2-MeTHF, 1.6 mmol furaldehyde, 4.8 mmol formaldehyde, 2.5mmol L-1 MgS04, 0.15 mmol L-1 ThDP, 168 U BAL, 1500 U GDH, 95 U FDH, NADH/NAD+1 mmol L-1 each... 

Fig. 8.137 InCb-catalyzed transformation of D-glucal to chiral furan diol OH ln(OTf)3 (10 mol %)...

The 7, i5-unsaturated alcohol 99 is cyclized to 2-vinyl-5-phenyltetrahydro-furan (100) by exo cyclization in aqueous alcohol[124]. On the other hand, the dihydropyran 101 is formed by endo cyclization from a 7, (5-unsaturated alcohol substituted by two methyl groups at the i5-position. The direction of elimination of /3-hydrogen to give either enol ethers or allylic ethers can be controlled by using DMSO as a solvent and utilized in the synthesis of the tetronomycin precursor 102[125], The oxidation of the optically active 3-alkene-l,2-diol 103 affords the 2,5-dihydrofuran 104 in high ee. It should be noted that /3-OH is eliminated rather than /3-H at the end of the reac-tion[126]. 

Timko and Cram were the first to prepare true crown ethers containing the furanyl subcyclic unit ° . Destructive distillation of sucrose yielded 2-hydroxymethyl-5-formyl-furan 7 in 41% yield. This could be reduced to the corresponding diol in 91% yield by treatment with sodium borohydride. Reaction of the diol with tetraethylene glycol dito-sylate, and potassium t-butoxide in THE solution afforded the crown in 36% yield. The approach is illustrated below as Eq. (3.26). 

Epoxides (oxirans) and 1,2-diols can also be looked upon as disguised ketones capable of being unmasked by acids. Since its development by Spencer et al49 the idea has been utilized by several other groups who used protic acids in work aimed at syntheses of methyl lambertianate,50 a rare furanoid fatty acid from an Exocarpus species,51 and a terpenoid furan,... 

A practical method for the synthesis, resolution and determination of the absolute configuration of 9,9 -binaphtha(2,l- >)furanyl-8,8 -diol was reported as shown below <06TS1275>. A rearrangement of 4-acetoxy-9-furanylnaphtho[2,3- >]furans to tetracyclic naphthodifurans was achieved under acidic conditions <06TL4117>. 

Disubstituted- and 2,3,4-trisubstituted-furans are provided by oxidation or oxidation/acid-induced cyclization of the corresponding 2-butene-l,4-diols. These methods have been successfully employed for the synthesis of hibiscone C <00SL363> and cristatic acid . 

Nucleophilic addition of furan to nitrone occurs upon treatment with trimethyl-silyl triflate (TMSOTf) (586, 587). Catalyzed TMSOTf stereoselective addition of 2-[(trimethylsilyl)oxy]furan to chiral nitrones was carried out in a short synthesis of [IS (la, 2[), 7f>, 8a, 8aa)]-l,2-di(t-butyldiphenylsilyloxy)-indolizidine-7,8-diol (588). Addition to N -gulosyl-C-alkoxymethyl nitrones led to the synthesis of the core intermediate of polyoxin C (218). 

A distannation product of 2-butyne-l,4-diol oxidatively cyclizes to provide 3,4-bis(stannyl)furan, which then undergoes palladium-catalyzed cross-coupling with an aryl iodide to give 3,4-diarylfuran (Scheme 31).152,153... 

This rearrangement of allylic acetals can also be used for furan annelations, in which the formation of the new tetrahydrofuran ring is coupled with ring enlargement of the starting ring.3 The same dr-fused bicyclic tetrahydrofuran is formed from either one of the cis- or mwr-allylic diols used as starting materials. 

The reaction appears to be general and the additions are regiospecific and stereoselective. The product from the reaction with 2-propanol has been used for the synthesis of cis-chrysanthemic acid,8 and the product with methanol has been used for the construction of novel 2, 3 -dideoxy-3 -hydroxymethylnucleosides.9 In addition, ethane-1,2-diol provides the expected photoadduct as a 1 1 mixture of the two possible diastereoisomers, and these can be easily separated as their acetonides, to provide compounds with three contiguous chiral centers emanating from furan-ones with only one chiral center.9 More recently, we have shown that photoinduced-... 

Isosorbide is a rigid diol with two non-equivalent hydroxyl groups (endo-5 and exo-2) and two tetrahydro-furan rings in its structure ... 

Finally, a novel investigation on furanic polyesters is being carried out with the aim of arriving at powers with regular structure by solution reactions involving the diacid dicmoride 11b or similar compounds and various diols and diphenoTs (32). Thus, for example, with 1,8-octandiol a medium-DP polyester was obtained with a melting point of about 190°C. 

NaOH solution of the diol and an organic solution of the dihalide in the presence of a phase-transfer catalyst (31). The best results were obtained with dichloro-p-xylene as comonomer and gave polymers with the furanic-aromatic structure 26 ... 

Surprisingly little information is available on simple furanic urethanes and only one investigation on thermoplastic polyurethanes containing the heterocycle (34). The latter made use of difurylic diisocyanates with aliphatic diols to amve at structures like ... 

In order to gain a better insight into these problems, a fundamental study of simple mono- and di-urethanes of the furan series was undertaken. This included the determination of their structure, properties and stability (35) and the mechanism and kinetics of their formation. The combinations investigated were furan alcohols and diols with aliphatic, aromatic and furanic isocyanates and the latter mono- and bis- derivatives with aliphatic and arylalkyl alcohols and diols. The furanic isocyanates prepared included 9 and those given below ... 

In their pioneering work. Just and co-workers have described many interesting transformations of the Diels-Alder adducts of furan to methyl nitroacrylate (77 + 77 ) and to dimethyl acetylenedicarboxylate (53). The mixture of racemic adducts 77 + 77 was hydroxylated into the exo-cis-diols 125 + 125 , separable by crystallization. Treatment of the isopropylidene acetal obtained from 125 with diazabicyclo[5.4.0]undec-5-ene (DBU) gave a high yield of alkene 126. Ozonolysis followed by a reductive work-up with dimethylsulfide, then with NaBH4, gave a mixture of epimeric triols 127. Cleavage with sodium periodate afforded 2,5-anhydro-3,4-0-isopropylidene-DL-allose (128) in 15 % yield, based on methyl 2-nitroacrylate used. TTie same allose derivative was obtained from adduct 53. ... 

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