Patent GB-695789-A (GB)
Title: Oxygen containing propene derivatives
Inventor: HALL REGINALD HAROLD
Filed: 1950-02-11
Abstract: Compounds RO-CH2-CHR3-CH(OR1) (OR2), in which R, R1 and R2 are alkyl, aryl, aralkyl or cycloalkyl radicles and R3 is hydrogen or alkyl are pyrolized with a cracking catalyst in a homogeneous phase at 200-450 DEG  C., preferably 325-425 DEG  C. to give di-ethers RO-CH2-CR3=CH(OR1) and/or an acrolein acetal CH2= CR3-CH(OR1)(OR2). Preferably the starting compounds are of formula R3O-CH2-CHR6-CH(OR4)(OR5), where R3, R4 and R5 are alkyl radicles and R6 is hydrogen or methyl.  Liquid or vapour phases may be used and the catalyst is preferably acidic or one which gives rise to acidic materials, e.g. sulphuric acid, di-isopropyl sulphate, dimethyl sulphate or ethyl hydrogen sulphate.  Quinoline is also specified as a catalyst.  Stabilizing agents, e.g. pyridine, quinoline or collidine may be present.  More severe reaction conditions, e.g. longer contact times or higher temperatures, favour the production of acetal since under these conditions the di-ether is isomerized to an acetal which may or may not be the same as that derived from the starting material, depending upon the values of the R's.  Products are preferably separated by vacuum fractional distillation.  Both products may be reconverted to starting material by reaction with the necessary hydroxy compound in the presence of an acid catalyst, so that the reaction may be operated to yield either acetal or di-ether by reconverting the appropriate by-product to fresh starting material.  The di-ethers may be hydrogenated to the corresponding propylene glycol ethers. Typical of specified products are acroleindibutyl and dibenzyl acetals, 1,3-dimethoxy-, 1,3-diisopropoxy-, 1,3-dibenzyloxy-, and 1-butoxy-3-ethoxy-prop-1-ene.  The di-ethers are stated to be new compounds as are certain of the acetals, e.g. those of formula CH2=CH-CH(OR)(OR), where R is n-propyl, isopropyl, butyl or benzyl. In examples: 1,1,3-trimethoxy propane, diisopropyl sulphate and (1) pyridine and (17) quinoline yield acrolein dimethyl acetal and 1,3-dimethoxypropene, the latter being hydrogenated in (1) over Raney nickel; 1,1,3-tri-n-butoxypropane, diisopropyl sulphate and (2) pyridine and (19) quinoline yield acrolein di-n-butyl acetal and 1,3-di-n-butoxypropene which is hydrogenated in (2); 1,1-butoxy-3-ethoxypropane, diisopropyl sulphate and (3) pyridine yield acrolein dibutyl acetal and in (16) with quinoline yield the acetal and 1-butoxy-3-ethoxypropene which is hydrogenated; 1,1-diethoxy-3-butoxy-propane, diisopropyl sulphate and quinoline in (4) yield acrolein diethyl acetal and 3-butoxy-1-ethoxy-prop-1-ene which is hydrogenated; 1,1,3-triethoxypropane and (5) and (18) diisopropyl sulphate and quinoline, (6) dimethyl sulphate and pyridine, (7) and (8) conc. sulphuric acid, (9) and (10) diisopropyl sulphate and pyridine and (15) quinoline yield acrolein diethyl acetal and 1,3-diethoxypropene, the acetal being converted to starting material in (8) and the diether hydrogenated in (10); and (11) 1,1,3-tri-n-propoxy, (12) -tri-isopropoxy-, (13) -tribenzyloxy-, and (14) -triethoxy-2-methyl-propane with diisopropyl sulphate and quinoline yield the respective acetals and ethers, those from (11) and (12) being hydrogenated.  Except in (6)-(10) nitrogen is present. Alcohols are often obtained as by-products.  According to the first Provisional Specification the catalyst may be homogeneous or heterogeneous, including solid catalysts such as acid-treated clays, silica gel alone or with an alkali earth or earth oxide, alumina or aluminium phosphate and the second Provisional Specification includes examples in which 1,1,3-triethoxypropane is treated with (8) ammonium sulphate and (10) fuller's earth.  The starting materials are made by reacting acrolein or a beta-alkoxypropionaldehyde with the desired hydroxy compound, e.g. methyl, ethylhexyl or cyclohexyl alcohols or phenol and details are given of the preparation of 1,1-dibutoxy - 3 - ethoxy -, 1,1 - diethoxy - 3 - butoxy -, 1,1,3 - tri - n - propoxy -, 1,1,3 - triisopropoxy -, 1,1,3 - tribenzyloxy and 1,1,3 - triethoxy - 2 - methyl-propane.