Distillation Kugelrohr

In a typical case, ethylamine is allowed to react with ethylene oxide to produce N-ethyldiethanolamine (5). The latter is then treated with additional ethylene oxide to afford N,N-di(polyoxyethylene)ethylamine (6) where the sum a -t b is 3. This material is then stirred at room temperature for 3 h with toluenesulfonyl chloride and powdered sodium hydroxide in dioxane solution. After filtration and Kugelrohr distillation, N-eth-ylmonoaza-15-crown-5 is isolated in 75% yield as illustrated below in Eq. (4.7). 

In this method, an oligoethylene glycol is treated with 0.3 eq. of sodium bromoace-tate in methanol. The resulting monocarboxylic acid salt is then treated with toluene-sulfonyl chloride, sodium carbonate and dioxane. After heating the reaction mixture at 50° for an hour, the product was obtained either by Kugelrohr distillation or extraction. The two compounds produced in the reaction below (i.e., n = 1 and n = 2) were formed in 38% and 42% yields respectively . 

Method A i01 Equivalent amounts of a 1,2,3-benzothiadiazole. sulfur (as S8) and DABCO were added to Decalin (10 mL per gram of benzothiadiazole) and N2 was passed through the mixture. The mixture was heated at 160-190 C until N2 evolution ceased (20-90 min). It was cooled and the Decalin was removed by Kugelrohr distillation at 50 C/0.5 Torr. The residue was twice triturated with CH2C12 and the extracts were combined and filtered from sulfur. Chromatography (silica gel, 1 % EtzO/hcxanc) gave the product. The preparations were carried out on a scale of 0.25-10.0 g benzothiadiazole. 

Na2S04. Removal of the solvent, followed by Kugelrohr distillation, affords the /5-trimcthylsilyloxy ketones. Solvolysis in 5 mL of CH3OH with a catalytic amount of hydrochloric acid for 5-10 min at 20 %, neutralization with NaHCO v and workup with C H.Cl, as described in Method A, furnishes the /i-hydroxy ketones which are purified by distillation or crystallization. 

This procedure provides a convenient method for the esterification ol a wide variety of carboxylic acids. The reaction proceeds smoothly with sterically hindered acids6 and with acids which contain various functional groups. Esters are obtained in high purity using Kugelrohr distillation as the sole purification technique. In cases where traces of dichloromethane present no problems, the crude product is usually pure enough to be used directly in subsequent reactions. Methyl and ethyl ethers of phenols may also be prepared by this procedure (see Note 8). 

E. l-Amino-2-phenylaziridine (Note 23). If the pentane solution from Step D is removed on a rotary evaporator at room temperature, 7.5-7.7 g. (82-85%) of l-amino-2-phenylaziridine, suitable for preparative use, is obtained. Kugelrohr distillation of this material on a 1-2 g. scale (0.01 mm./60-65° oven temperature) (Note 24) gives a recovery of over 90% (Notes 23 and 25). 

The checkers found that although the chromatographed product was a light yellow oil, it was analytically pure. Kugelrohr distillation was required to obtain a colorless oil. 

The crude product was purified by Kugelrohr distillation (98-103°/0.2 mm) followed by column chromatography (55-mm diameter column, 200 g of silica gel, elution with pentane/EtOAc, 50/1), and another Kugelrohr distillation. 

Kugelrohr distillation ovens manufactured by Biichi Glasaparatefabrik are available from Brinkmann Instruments, Inc., Wcstbury, New York. 

After a mixture of powdered 1-formylnaphthalene (48) and powdered KOH was kept at 100 °C for 5 min, water was added to the reaction mixture, which was filtered to give l-(hydroxymethyl)naphthalene (50), after Kugelrohr distillation, in 38% yield. The filtrate was acidified with concentrated HCl and filtered to... 

The homoallylation is applicable to multigram-scale experiments (Scheme 15) [36]. In the presence of 3mol% of Ni(acac)2, a mixture of 25 mmol of benzaldehyde, 50 mmol of Et3B, and 50 mmol of isoprene provides anti-3-methyl-l-phenyl-4-pentenol in 92% yield (4.1 g) with excellent 1,3-anti stereoselectivity. The product is purified by means of a single Kugelrohr distillation of the reaction mixture after an appropriate aqueous workup. 

The compound exploded during Kugelrohr distillation at about 1 millibar, temperature not stated but probably about 100°C. 

During the Kugelrohr distillation a forerun of 3-4 mL is collected and discarded. 

Diethyl phosphorochloridite (0.714 ml, 5 mmol) was added dropwise to a stirred solution of 2,5-dimethoxytetrahydrofuran (0.65 ml, 5 mmol) in methylene chloride at 0°C under an argon atmosphere. The solution was then stirred at room temperature for 12 h, after which the solution was concentrated under reduced pressure and the residue subjected to Kugelrohr distillation (120°C/0.03 torr). There was in this manner isolated the pure diethyl 5-methoxytetrahydrofuran-2-ylphosphonate (0.475 g, 48%) as a colorless oil. 

The polymerization catalysts that are preferred because of their selectivity are the alkali metal (especially cesium) carbonates, tetraalkylammonium and bis(triphenylphosphoranylidene)ammonium (PPN) chlorides and bicarbonates (Table 4.2). Undesired side reactions are minimized by using relatively low (< 5% by weight) catalyst levels. Under these conditions, the fraction of cyclic oligomer was usually 5% or less and was easily removed from the desired polymer by Kugelrohr distillation. Conversions of 5 were essentially quantitative as judged by product weights and lack of detectable amounts of unreacted monomer by GPC. 

Tetramethylammonium chloride (2 mg) and 5 (1. Og) were placed in a vial, sealed, and heated in an oil bath at 107°C for 65 h. H-NMR analysis of the colorless, viscous grease showed the ratio of signals at 4.6 and 3.90ppm as ca. 60/1. The small amount of cyclic dimer formed (GC anlaysis) was removed by Kugelrohr distillation (up to 100°C/0.05 mm). 19F-NMR featured the internal/ terminal CF2CH20 group ratio as ca. 83/1. Size-exclusion chromatography showed the major peak with Mn, =26,700 and Mw =52,800, consistent with condensation polymer 7. 

Hayek et al. (1990) reported the identification of 14 samples of birch bark tar of Chalcolithic to Early Iron Age date from sites in Austria and Denmark. In this study, authentic tars from bark samples of a number of different species (e.g., birch, oak, alder, hazel, elm and so on) were produced under laboratory conditions (using Kugelrohr distillation) and compared with the aged samples... 

Caution If a sufficiently high vacuum is not maintained, the increased temperature (pot temperatures >100-110°C) required for distillation may cause thermal decomposition of 2 and evolution of hydrogen chloride. The checkers observed that 2 had bp 95-100°C at 0.5 mm. Kugelrohr distillation (85-100°C at 0.3-0.5 mm) of the product in two batches can also be employed. 

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