Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts

The overall goal of this procedure is to demonstrate the preparation of unknowns from potassium, organo, tri fluoro, borate salts, and acyl chlorides. This is accomplished by first converting the canal tribo salt to a more reactive dichlorine species using boron tri chloride. The second step is to react the organochlorine species with an asal chloride to form the desired I unknown product.

Next, the workup is performed on the reaction solution to remove inorganic impurities. The final step is purification and characterization of the final product. Ultimately, this method allows for the straightforward preparation of from potassium, kinal, tri fluoro, orate salts, and acyl chloride starting materials.

The main advantage of this technique over existing methods, such as addition of metal aides to AAL chlorides, followed by oxidation to the corresponding unknown, is that a wider variety of functional groups are well tolerated and purification of synthetic intermediates is not necessary. Demonstrating the procedure will be Cassandra Taylor, a graduate student in my research laboratory. First way, 0.15, millimoles of the desired potassium kinal TLU salt on an analytic balance and add it to a clean vial fitted with a magnetic stir bar using a glass plunger syringe fitted with a needle add 0.5 milliliters of anhydrous chloro methane to the vial to afford a 0.3 molar solution of tri fluoro borate.

Using a glass syringe add 0.15 millimoles of one molar boron tri chloride solution, A dropwise to the reaction vessel at ambient temperature with stirring. After sealing the vial with a cap, hold the reaction vessel such that the solution is below the waterline in a sonicate. Then sonicate the solution for 30 seconds at 20 degrees Celsius, and a frequency of 40 kilohertz.

After sonication, stir the reaction solution at room temperature for an additional 20 minutes. Following reaction completion add 0.1, millimoles of the desired acyl chloride to the vial at ambient temperature with stirring. After replacing the cap, stir the reaction solution at ambient temperature for 30 minutes.

To monitor the reaction progress by thin layer chromatography or TLC spot the reaction solution and appropriate acyl chloride standard on the starting line of the TLC plate. Using A TLC spotter, develop the TLC plate in a suitable mobile phase. Then visualize the developed plate under UV light and use a pencil to mark any visible spots.

After confirming reaction completion by TLC, quench the reaction by adding one milliliter of cold water to the vial. Using a pasture pipette, transfer the solution to a clear separatory funnel. Further dilute the contents of the separatory funnel with 10 milliliters of cold water.

Then add 15 milliliters of ethyl acetate and extract the product into the top ethyl acetate layer. Discard the bottom aqueous layer and wash the organic layer. One additional time with 10 milliliters of water.

After washing the organic layer with 10 milliliters of brine collected into a clean erlenmeyer flask and dry with magnesium sulfate, filter the solution into a clean, round bottom flask using gravity filtration using thin layer chromatography. Determine a suitable mobile phase for flash chromatography purification of the product. Prepare a column containing silica wet with the appropriate mobile phase.

Then add a layer of sand to the top of the column in order to avoid disturbing the silica upon addition of the product and ellu. Next, evaporate the workup solution using a rotary evaporator with a bath temperature at 40 degrees Celsius and the rotation set to 120 revolutions per minute. When finished, dissolve the contents of the flask in two milliliters of mobile phase.

Carefully load the solution evenly onto the column, allowing some solvent to elute such that the product is on the silica. After repeating the previous step with a small amount of mobile phase, fill the column with the mobile phase. Use air pressure so that the ellu flows through the column at a suitable rate, and collect the fractions in test tubes.

Following purification. Spot each of the column fractions on A TLC plate with the acyl chloride standard as a reference. After developing the TLC plate with the appropriate mobile phase, mark any spots visible under UV light, noting that the product is expected to have a lower retention factor than the acyl chloride standard.

Collect all fractions containing visible spots into a large round bottom flask. After evaporating the solvent using a rotary evaporator, dry the material collected under high vacuum for two hours if required. Further, purify the product by dissolving it in di chloro methane and loading it onto a silica column.

Wet with pentane elute one to two column lengths of pentane through the column and collect into a waste beaker. Elute the pure unknown product from the pentane column. Using ethyl ether, collect the ellu in a separate round bottom flask, then evaporate the solvent using a rotary evaporator.

After drying under vacuum, obtain approximately 10 milligrams of product for characterization by nuclear magnetic resonance or NMR spectroscopy. At this point, characterize and assess the purity of the final product using proton and carbon NMR spectroscopy. Use infrared spectroscopy to identify the characteristic carbon peak of the unknown product, which should appear between one thousand six hundred and one thousand six hundred fifty inverse centimeters due to electron delocalization from the adjacent triple bond.

Finally, determine the molecular mass of the product and further validate the identity using high resolution mass spectrometry. Initial efforts were focused around the preparation of ione one A from phenyl acetylene, tri fluoro, S one, and benzoyl chloride. The optimization steps performed including screening of various Lewis acids solvents, as well as examination of the effect of water on the reaction are shown here.

The scope of the reaction has been explored by submitting phenyl acetylene trior abate to the optimized conditions in the presence of a variety of acyl chlorides, modest to excellent yields may be obtained depending on the nature of the AOC chloride substrate selected. Examples of other kinal tri fluoro orate salts that can be employed in the preparation of odes under the developed conditions are illustrated here. Derivatives of phenyl acetylene, tri fluoro bate bearing electron donating sub afforded the corresponding unknown products in good to excellent yields.

While atic derivatives of Alcon tri fluoro bate salts proved to be slightly less reactive, affording modest yields. After watching this video, you should have a good understanding of how to prepare, purify, and characterize various unknowns in an efficient and straightforward manner.