Acrylic acid molecular sieves

B. Ethyl a-(bromomethyl)acry late. In a nitrogen-flushed, 1-L, round-bottomed flask equipped with a magnetic stirrer, Dean-Stark trap, and condenser are placed 42.0 g (0.25 mol) of a-(bromomethyl)acrylic acid and 300 mL of benzene. Approximately 50 mL of a binary azeotrope of benzene and water is distilled (Note 7). The Dean-Stark trap is removed and 100 mL of absolute ethanol (Note 8) and 1 mL of concentrated sulfuric acid are added slowly. The contents of the flask are boiled in a nitrogen atmosphere for 36 hr, the condensate being passed through 100 g of molecular sieves (Linde 3A) before being returned to the flask. About 125 mL of a mixture of benzene and ethanol is removed from the reaction... 

Chiral Lewis Acid. These chiral titanium reagents are widely used as chiral Lewis acid catalysts. The Diels-Alder reaction of methyl acrylate and cyclopentadiene affords the endo adduct in moderate enantioselectivity when a stoichiometric amount of the chiral titanium reagent (5) is employed (eq 6). Use of 3-(2-alkenoyl)-l,3-oxazolidin-2-ones as dienophiles greatly improves the optical purity of the cycloadduct when the 2-phenyl-2-methyl-1,3-dioxolane derivative (6) is used as a chiral ligand. Most importantly, the reaction proceeds with the same high enantioselectivity for the combination of various dienophiles and dienes even when 5-10 mol % of the chiral titanium reagent is employed in the presence of molecular sieves 4A (eqs 7 and 8). ... 

Ethylene has been separated from ethane by a silver nitrate solution passing countercurrent in a hollow fiber poly-sulfone.165 This separation has also been performed with the silver nitrate solution between two sheets of a polysilox-ane.166 A hydrated silver ion-exchanged Nafion film separated 1,5-hexadiene from 1-hexene with separation factors of 50-80.167 Polyethylene, graft-polymerized with acrylic acid, then converted to its silver salt, favored isobutylene over isobutane by a factor of 10. Olefins, such as ethylene, can be separated from paraffins by electroinduced facilitated transport using a Nafion membrane containing copper ions and platinum.168 A carbon molecular sieve made by pyrolysis of a polyimide, followed by enlargement of the pores with water at 400 C selected propylene over propane with an a-valve greater than 100 at 35°C.169... 

Some thermally forbidden [2 + 2]-cycloaddition reactions can be promoted by Lewis acids1-6. With chirally modified Lewis acids, the opportunity for application in asymmetric synthesis of chiral cyclobutanes arises (for a detailed description of these methods see Sections D.l. 6.1.3.. D.l. 61.4. and references 7, 28-30). Thus, a chiral titanium reagent, generated in situ from dichloro(diisopropoxy)titanium and a chiral diol 3, derived from tartaric acid, catalyzes the [2 + 2]-cycloaddition reaction of 2-oxazolidinone derivatives of a,/ -unsalurated acids 1 and the ketene thioacetal 2 in the presence of molecular sieves 4 A with up to 96 % yield and 98% ee. Fumaric acid substrates give higher yields and enantiomeric excesses than acrylic acid derivatives8. Michael additions are almost completely suppressed under these reaction... 

Applications of chirally modified titanium Lewis acids have been reported most cases use various acetal diols derived from tartrate as the chiral auxiliary26 33,31 90. Various methods of catalyst preparation are known, as well as the use of different types of dienes (open-chained, cyclopentadiene) and dienophiles (acroleins, acrylates, crotonates, fumarates and amides derived from oxazolidinone), including intramolecular cycloaddition30. Addition of 4 A molecular sieves can improve asymmetric induction31,34 (as observed with the Sharpless epoxidation, loc. cit 31 in ref 6) and shows remarkable solvent effects on enantioselectivity. This method has been applied to the asymmetric Diels-Alder cycloaddition of cyclopentadiene and open-chain dienes to acrylamides28, 35. 

Amide formation. o-Halophenylboronic acids catalyze the Diels-Alder reaction of acrylic acid as well as condensation of carboxylic acids with amines at room temperature (in the presence of 4A-molecular sieves). ... 

In a dry flask were added 855 mg tosylamide (5 mmol), 84 mg DABCO (0.75 mmol), and 58.5 mg La(0Tf)3-H20 (0.1 mmol) together with 900 mg 4-A molecular sieves. Then 2.5 mL wo-PrOH, 505 fiL benzaldehyde (5 mmol), and 450 /u-L methyl acrylate (5 mmol) were added, and the reaction mixture was stirred for 48 h at ambient temperature. The mixture was Altered through a thin layer of Celite, which was rinsed three times with 10 mL wo-PrOH. The solvent was evaporated, and to the crude mixture were added 25 mL methanol and 10 mL 1 M sulfuric acid. The solution was stirred for 1 h, and then methanol was evaporated. The remaining acidic solution was diluted with water and extracted with dichloromethane (3 x 30 mL). The organic phase was then successively washed with saturated NaHCOs, 1 M NaOH, water, and saturated NaCl solution and dried over Na2S04. Evaporation of the solvent gave 1.38 g pure methyl Q -methylene-)8-[(/ -toluenesulfonyl)-amino]-3-phenylpropionate as a white crystalline material, in a yield of 80%, m.p. 76-77°C. 

Materials. N,N-Dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) were stirred over powdered calcium hydride overnight, distilled under reduced pressure, and then stored over 4-A molecular sieves. 4-Aminobenzhydrazide (5) was prepared from methyl 4-aminobenzoate and hydrazine monohydrate according to the reported procedure (6). 4,4 -Thiobisbenzenthiol (6) and isophthalic acid (7) were purified by reciystdlization. Phenyl acrylate and 4-nitrophenyl acetate were prepared by the reactions of acryloyl chloride or acetyl chloride with phenol or 4-nitrophenol in the presence of triethylamine and tetahydrofuran, respectively. TrieAylamine (TEA) and tetahydrofuran (THF) were purified by the usual method. Other reagents and solvents were obtained commercially and used as received. 

---