Trans-1,3-Cyclobutanediol

B. Cyclopropanecarboxaldehyde. A 50-mL distilling flask equipped with a receiver cooled to -20°C with a dry ice-methanol bath is charged with 34 g (0.39 mol) of a crude mixture of both cis-and trans-1,2-cyclobutanediol and 10 pL of boron trifluoride butyl etherate (Note 8). The mixture is heated to 230°C with a metal bath. Drops of liquid appear on the condenser, and the aldehyde and water distil into the receiver. The temperature of the distillate oscillates between 50°C and 100°C. Each time the distillation stops, 5-10 pL of boron trifluoride butyl etherate is added to the distilling flask (Note 9). The distillate is transferred into a separatory funnel and sodium chloride is added. The organic layer is decanted and the aqueous layer is extracted three times with 25-mL portions of methylene chloride. The combined organic solution is dried over sodium sulfate, and the solvent is removed by distillation through a 15-cm, helix-packed, vacuum-insulated column. The residue con-... 

Both CIS- and trans-1,2-cyclobutanediols rearrange under the influence of acid to give the corresponding cyclopropanecarboxaldehydes or ketones in high yields (equation 165) " ... 

In the case of 1-alkylated 1,2-cyclobutanediols, the tertiary hydroxyl is the preferred or exclusive leaving group. With 1,2-dialkylated diols, the trans isomers were normally found to rearrange somewhat more easily than the cis compounds. For instance, trans-1,2-dimethyl-l,2-cyclobutanediol (243) underwent immediate quantitative ring contraction to (1-methylcyclopropyl) methyl ketone (244) upon treatment with boron trifluoride etherate at room temperature while the ring contraction of the cis isomer (245) was observed only on heating at 70°C for 5 min in the presence of BF3 and Et20 (equation 166) . 

After the butyl alcohol was removed, the polymers were built up by heating the melt under reduced pressure. Since these polyformals of aliphatic diols had very low melting points (below 75° C.), their utility was limited. Apparently, no higher melting points have been reported for polyformals. In attempts to obtain higher-melting polyformals, the following alicyclic diols were used cis-, trans-, and 1 to 1 cis-/trans- mixture of 2,2,4,4-tetramethyl-l,3-cyclobutanediol (I) trans-1,4-cyclohexanediol (II) tmiw-l,4-cyclohexanedimethanol (III) and 2,5- or 2,6-norbomanediol (IV). 

Materials. 2,2,4,4-Tetramethyl-1,3-cyclobutanediol. The diol was a commercial product (Tennessee Eastman Co.). Unless otherwise indicated, the diol consisted of a cis-/trans- mixture with about a 1 to 1 isomer ratio. The cis-isomer was obtained from the isomer mixture by transforming the trans- isomer into an unsaturated aldehyde with aqueous sulfuric acid (4). The mrw-diol was obtained by preparing the diformate of the isomer mixture, separating the trans-derivative from the cis- derivative by recrystallization, and converting the transdiformate to the diol by methanolysis (5). 

Paraformaldehyde Method. 2,2,4,4-Tetramethyl-1,3-cyclobutanediol. A 2-liter, three-necked flask was fitted with a glass stirrer, thermometer, and Dean-Stark trap which was filled with distilled cyclohexane and attached to a water-cooled condenser. In the flask were placed 216 grams (1.5 moles) of 2,2,4,4-tetramethyl-l,3-cyclobutanediol (1 to 1 cis-/trans- mixture), 52.2 grams (1.65 moles, if 95% pure) of paraformaldehyde, 1200 ml. of distilled cyclohexane, and 0.20 gram of methanedisulfonic acid in a 10 to 25% aqueous solution. (The catalyst solution had been treated with Darco G-60 to remove all color.) While this mixture was stirred at 60° C., the paraformaldehyde depolymerized to formaldehyde, which reacted with the diol. Complete reaction of these two components was indicated when they had gone into solution. This required about 1 hour. 

The solid-phase method of building up polyformals is applicable only to high-melting polymers. The required melting point is not known, but the poly-formal of trarw-l,4-cyclohexanediol melted at 206°—10° C. and that of the cis-/ trans- mixture of 2,2,4,4-tetramethyl-l,3-cyclobutanediol melted appreciably higher. The solution method did not appear to be applicable to building up the polyformals of these two diols, since inherent viscosities below 0.4 were obtained. The solution method may be most applicable to primary diols, such as cyclohexanedimethanol and decanediol, which gave polyformals with inherent viscosities of 0.9. 

The pinacol rearrangements of several cyclobutanediols, mostly induced by BFs-OEta, have been examined by Conia. The reactions of symmetrically substituted materials occurred with high specificity and yield. Both isomers cis and trans) gave the same product in instances where this question was examined. As shown in equation (17), for the substituents R = H, alkyl or phenyl, only ring contraction was observed, while equally regiospecific formation of the cyclobutanone product was found for the substituents R = allyl or vinyl. 

Another copolyester is prepared from two diols, CHDM and 2,4,4-tetramethyl-l,3-cyclobutanediol (TMCD). These diols, which have cis and trans con-hgurations, are reacted with dimethyl terephthalate to give an amorphous, transparent copolyester [36]. This amorphous copolyester features good chemical and heat resistance, which make this copolyester suitable for hot-fill cosmetics packaging, personal care and fragrance packaging. These polymers are available from Eastman Chemical under that Tritan trade name. The structure of CHDM/TMCD copolyester is depicted in Fig. 1.21. 

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