Schlenk tubes

In a flame-dried Schlenk tube 0.37 g(1.88 mmol) of (-)-3-exo-(dimethylamino)isoborneol (C) and 200 mL of dry toluene are placed under an atmosphere of argon. 27 mL of 4.2 M diethylzinc (113 mmol) in toluene are added and the resulting solution is stirred at 15°C for 15 min. After cooling to — 78°C, lOg (94.2 mmol) of benzaldehyde are added and the mixture is wanned to O C. After stirring for 6 h, the reaction is quenched by the addition of sat. NH4C1 soln. Extractive workup is followed by distillation yield 12.4 g (97%) 98% ee [determined by HPLC analysis. Baseline separation of rac-1 -phenyl-1 -propanol was achieved on a Bakerbond dinitrobenzoyl phenylglycine column (eluent 2-propanol/hexanc 1 3 flow rate l.OmL/ min detection UV 254 nm)] [a] 0 —47 (c = 6.11, CHC13). 

Via the Z-enolate an oven dried Schlenk tube equipped with a rubber septum is flushed with argon and charged with 0.66 mL (1.0 mmol) of butyllithium (1.5 N in hexane). The Schlenk tube is cooled to 0°C (icc/salt) and 0.12 g (1.1 mmol) of diisopropylaminc are added slowly by a syringe. This mixture is stirred for 15 min and the rubber septum is replaced by a glass stopper. The hexane and the excess diisopropyl-amine are removed under reduced pressure. After the flask is filled with argon the stopper is replaced with a septum and 0.47 g (4.3 mmol) of HMPA and 2.5 mL of THF are added. This solution is immediately cooled to — 78 °C and 0.14 g (1.1 mmol) of tert-butyl propanoate arc added quickly by syringe. After stirring for... 

Today, the glassware required consists of either a round-bottom flask or a Schlenk tube serving as the reaction chamber. This chamber is equipped with a magnetic stirbar and a Teflon high-vacuum valve (or glass stopcock) which provides for easy vacuum control after attachment to a vacuum line (Fig. 8.7). 

Methyl 3-oxobutanoate, available from Nakaral Chemicals (the checkers used ester purchased from Aldrich Chemical Company, Inc.), Is distilled over molecular sieves 4A under argon and stored in a 200-mL Schlenk tube. It is degassed by three treeze-thaw cycles before use. 

Watt and Drummond, were considered to be inert for C-C bond forming reactions. However, by the expedient of transmetallation to Cu, Ni, Zn, Li, and Al, methodologies for the stereoselective synthesis of olefins and dienes, as well as unusual heterocycles, aromatics and their ring-annulated products are now available which are beginning to make impact on material science, e. g. synthesis of pentacenes and polyphenylenes. Takahashi and Li provide evidence that, with further developments in transmetallation and handling the zirconacycles outside of the Schlenk tube techniques, synthetic utility will increase and new catalytic reactions will be developed. 

Sixty years ago, organic chemists were struggling with the preparation and observation of properties of organolithiums today, metallation chemistry is routinely executed on gram and multi-ton scale. Since chemists are recognized for their intense level of curiosity and pride in experimental achievement, the real or apparent intricacies associated with the preparation and use of Zr and Ti reagents that appear to be bizarre, unavailable, and/or relegated to the Schlenk tube will be overcome. May this volume be a hallmark in this quest. 

A 50 mL Schlenk tube was dried overnight in a oven at 150°C, cooled under vacuum and flushed with nitrogen. 

The Schlenk tube was filled with [Ru(allyl)2(COD)n] (6 mg), ((S j-BiNAP) (21 mg) and purged twice using vacuum/nitrogen cycles. Anhydrous acetone was added (2 mL) to give a white suspension. The solution was stirred for 30 minutes at room temperature. 

The Schlenk tube containing the catalyst was filled with degassed methanol (20 mL) and methyl acetoacetate (100 xL) the brown suspension was placed under nitrogen. 

The Schlenk tube was connected to a low-pressure hydrogenation apparatus fitted with a gas burette system to measure the hydrogen consumed. The Schlenk tube was flushed through three cycles (reduced pressure/ hydrogen) and then placed under an atmospheric pressure of hydrogen. The burette was filled with 200 mL of hydrogen. 

In a Schlenk tube equipped with a magnetic stirrer bar were placed under nitrogen [Ru(benzene)Cl2]2 (5 mg), ephedrine (6.6 mg) and dry 2-propanol (5mL) previously degassed by three freeze-thaw cycles. The mixture was stirred for 20 minutes at 80 °C to give an orange solution which was allowed to cool to room temperature. 

In a second Schlenk tube were placed under nitrogen tert-butyl acetoacetate and dry 2-propanol (14 mL). The mixture was degassed and added to the first solution. Finally, degassed potassium 2-propylate solution (1 mL) was added. The resulting orange solution was stirred at room temperature. 

In a Schlenk tube equipped with a magnetic stirrer bar were placed (S,S)-1,2-bis(boranato(tert-butyl)methylphosphino)ethane (2) (131 mg) and dry toluene (4mL) under an argon atmosphere at 0°C. To this solution, trifluoro-methanesulfonic acid (0.22 mL) was added over a period of 5 minutes. 

In a Schlenk tube, equipped with a magnetic stirrer bar, were placed BisP (77 mg), bis(2-methylallyl)cyclooctadieneruthenium (II) (105 mg), and degassed //-hexane (2.5 mL) under an argon atmosphere. The mixture was stirred at 60 °C for 10 hours. 

N-(Trimethylsilyl)-S,-methyl-S-phenylsulfoximine (prepared as above) was dissolved in 15 mL of dry tetrahydrofuran and transferred by cannula into the Schlenk tube under nitrogen. 

The Schlenk tube was filled with [(COD)Rh(acac)] (3.1 g) and cycloocta-1,5-diene (1.30 g) which were dissolved in 15mL of dry tetrahydrofuran. To this orange mixture, the solution of HBF4.OEt2 in tetrahydrofuran (7.52 mL) was added. A brown precipitate appeared, giving a viscous solution, which was diluted with 40 mL additional tetrahydrofuran to allow the reaction to stir efficiently. 

Two 100 mL Schlenk tubes with magnetic stirrer bars... 

A sinter funnel with nitrogen inlet connected to the second dry Schlenk tube was filled with a pad of activated alumina which was cooled under vacuum and then flushed with nitrogen. The precipitate was filtered off through the pad of alumina under nitrogen. The solvent was removed under vacuum from the second Schlenk tube. 

A 25 mL Schlenk tube equipped with a magnetic stirrer bar was dried at 150 °C overnight, cooled under vacuum and then flushed with nitrogen. 

The Schlenk tube was filled with bisphosphinite ligand, (1R, 3R, 5R, 6S)-3,6-bis [bis (4 -fluorophenyl) phosphinooxy] bicyclo[3.2.0]heptane (6.7 mg), degassed methanol (3 mL) and (COD)2Rh 1 BF4 (5.25 mg). The reaction mixture was stirred at room temperature until all the material was dissolved (10 15 minutes) giving an orange solution. 

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