Kiigelrohr distillation

B. 1-Benzylindole. The slurry of indole sodium is cooled to 0° (ice bath), and 2.30 ml. (2.53 g., 0.02 mole) of benzyl chloride (Note 5) is added as rapidly as possible to the stirred mixture. The mixture is then stirred for 8-15 hours (overnight), during which time the ice in the ice bath melts and the temperature of the reaction flask gradually rises to room temperature. The mixture is then diluted with 15 ml. of water and extracted with three 25-ml. portions of ether. The combined ethereal extracts are washed with two 40-ml. portions of water and dried with anhydrous magnesium sulfate. After filtration the solvent is removed at reduced pressure, and 4.4 g. of crude 1-benzylindole is obtained as a liquid. After bulb-to-bulb distillation of this material in a Kiigelrohr oven [120-130° (0.0025 mm.)], crystallization of the distillate from 15 ml. of hot ethanol affords 3.46-3.61 g. (83-87%) of 1-benzylindole. A second crop amounting to 0.17-0.26 g. (4-6%) is obtained on concentration of the mother liquors to 6 ml. The total yield of 1-benzylindole, m.p. 43-44°, is 3.72-3.78 g. (90-91%) (Notes 6 and 7). 

Vinylic tellurides (generalprocedure) Elemental Te (0.6 g, 5.0 mmol) is added to a solution of the vinylic magnesium bromide (5.5 mmol) in THE (10 mL) under reflux and N2 atmosphere, and the reflux maintained for 20 min. The mixture is allowed to reach room temperature and then treated with n-butyl bromide (0.7 g, 5.0 mmol). After stirring for 10 min, the reaction mixture is cooled at 0°C, treated dropwise with saturated aqueous NH4CI, extracted with ether, dried (MgS04) and then evaporated. Kiigelrohr distillation of the residue under vacuum gives the vinyl alkyl tellurides as yellow liquids. 

Cyclopropanation of a,fi-unsaturated carbonyl compounds with dibromomalonates (typical procedure) To a mixture of diethyl dibromomalonate (0.95 g, 3 mmol) and methyl vinyl ketone (0.27 g, 3.1 mmol) is added dibutyl telluride (0.73 g, 3 mmol) under argon and with stirring. The exothermic reaction is completed within 1 h. The mixture is chromatographed on an AI2O3, column (70-230 mesh, elution with EtOAc), giving dibutyltellurium dibromide (1.01 g, 84%) and then l-acetyl-2,2-bis(ethoxycar-bonyl)cyclopropane, which is purified by Kiigelrohr distillation (0.59 g (86%) b.p. 88-90°C/0.08 torr). 

Method OP Neat n-dodecylphenyltellurium dibromide (0.53 g, 1.0 mmol) is heated at 230-250°C at 3 torr using a Kiigelrohr distillation apparatus. A colourless liquid distills which is identical to n-dodecyl bromide ( H NMR and GLC analysis) [0.25 g, (90%)]. (A red-brown residue seems to be mainly PhTeBr and on standing exposed to the ambient atmosphere solidifies to a grey solid PhTe(0)Br and the starting dibromide by IR and combustion analytical data.)... 

Methyllithium (4.0 mmol, 1.0 M in diethyl ether, 4.0 mL) was added to a suspension of CuCN (2.0 mmol, 0.18 g) in THF (10 mL) at -75°C. The reaction mixture was then stirred until a clear solution was obtained and allowed to warm to room temperature. The appropriate (Z)-vinylic telluride A (2.0 mmol) or B (1.0 mmol) was added and stirred for 45 min. The solution was cooled back to -75°C and the corresponding enone (2.2 mmol) was added. After 20 min, chlorotrimethylsilane (2.6 mmol, 0.60 g) diluted in THF (5 mL) was added. The reaction mixture was stirred for 1 h, allowed to warm to room temperature and then treated with 1 1 solution of saturated aqueous NH4CI and NH4OH (20 mL), extracted with ethyl acetate (3x20 mL), dried, evaporated and the residue was purified by Kiigelrohr distillation affording the silyl enol ethers. 

Irone (6-methyl-ionone, -trans-(a)-4/-[2,5,6,6-tetramethyl-cyclohex-2-yl]but-3z-en-2-one) [79-69-6] M 206.3, b 85-86°/0.05mm, 109"/0.7mm, dj 0.9340, n, 1.4998. If large amounts are available then fractionate through a Podbielniak column or an efficient spinning band column, but small amounts are distilled using a Kiigelrohr apparatus. The 4-phenyl-semicarbazone has m 174-175° (165-165.5°). [IR Seidel and Ruzocka HCA 35 1826 1952-, Naves HCA 31 1280 1948. Lecomte and Naves J Chimique Physique 53 462 1956]. 

Benzyi-l,3-dioxolane [101-49-5] M 164.2, b 98-99°/lmm, 110°/5mm, 137-138 /34mm, 240-242°/atm, d 1.087, no 1.532. Dissolve in CH2CI2, wash well with IM NaOH, dry over K2CO3, filter, evaporate and distil through a short path still (Kiigelrohr). It has also been purified by preparative gas... 

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