Patent GB-653764-A (GB)
Title: A process for the preparation of dihydropyran and derivatives thereof
IPC: C07D309/30
Filed: 1948-05-31
Abstract: Derivatives of 3 : 4-dihydro-1 : 2-pyran are stated to be useful as raw materials for the preparation of resinous polymerization products.  2 - (3 : 4 - Dihydro - 1 : 2 - pyranyl) ethers (many examples of which are listed) are particularly suitable for polymerization, or for co-polymerization with olefinic compounds containing a vinyl group (e.g. vinyl halides, vinyl esters of aliphatic carboxylic acids, vinyl ethers or acetals, olefinic hydrocarbons, or acrylic or substituted acrylic acids, esters, amides or nitriles), preferably in the presence of a polymerization catalyst (e.g. boron trifluoride, aluminium chloride or zinc chloride). p  The Specification as open to inspection under Sect. 91 comprises examples of the polymerization of the ethers, which may be carried out in bulk, in solution (e.g. in a lower aliphatic alcohol, an ether, an ester or a hydrocarbon), or in emulsion. The products are useful as ingredients of adhesives, resin-base varnishes, lacquers containing cellulose derivatives, inks and moulding compositions, as modifiers of other plastic compositions, for paper treatment (e.g. impregnation or lamination), and as binders for other fibrous compositions. Vinylidene halides are additionally specified for use in copolymerization, and titanium tetrachloride, ferric chloride, hydrofluoric acid, sulphuric acid, phosphoric acid, antimony pentachloride and iodine as polymerization catalysts.  This subject-matter does not appear in the Specification as accepted.ALSO:3 : 4 - Dihydro - 1 : 2 - pyran and derivatives thereof are manufactured by heating (e.g. to about 100-250 DEG  C., preferably about 150-225 DEG  C.) an unsaturated carbonyl compound, wherein the carbonyl carbon atom is directly attached by a univalent bond to an olefinic carbon atom, with a dissimilar unsaturated organic compound which contains at least one pair of interconnected olefinic carbon atoms which is separated by at least one intervening atom from any additional olefinic and any acetylenic carbon atoms that the molecule may contain, for a time sufficient to effect appreciable condensation of the reactants.  The reaction may be carried out with the reactants in the gaseous state, but preferably with the reactants maintained in the liquid state by the use of sufficiently elevated pressures (which may be autogenous or applied by the introduction of an inert gas), and is preferably effected in the presence of a polymerization inhibitor or antioxidant (e.g. an amine or especially a phenolic compound, e.g. hydroquinone).  The unsaturated carbonyl compound may be any compound containing the grouping <FORM:0653764/IV (b)/1> (wherein R represents hydrogen or an unsubstituted or substituted hydrocarbon radical and the olefinic bond may be in an open chain or a non-aromatic carbocyclic or heterocyclic ring which may or may not include the carbonyl carbon atom), but is preferably a compound of the general formula <FORM:0653764/IV (b)/2> (wherein each R1 represents hydrogen or an unsubstituted or substituted hydrocarbon group, preferably an alkyl, aryl, alkaryl, aralkyl or cycloalkyl group).  The other unsaturated organic compound may be of one of the following types: olefinic hydrocarbons, halogen-, nitro- and phosphorus-substituted olefinic hydrocarbons, salts, amides and nitriles of olefinic carboxylic acids, esters of olefinic carboxylic acids and carboxylic esters of olefinic alcohols and their sulphur-containing analogues, olefinic amines, olefinic acetals and thioacetals, heterocyclic compounds containing an olefinic bond in the ring or in a side chain, olefinic sulphides, thiones and sulphones, and especially ethers wherein one or both of the organic radicals attached to the ethereal oxygen atom contains an olefinic bond.  Examples describe the preparation of 2-(3 : 4-dihydro-1 : 2-pyranyl)-isobutyl, vinyl, methyl and phenyl ethers and phenyl thioether, and 2 - methyl - 2 - carbomethoxy -, 2 : 5 - dimethyl - 2 - phenyl -, 2 - methoxy - 4 - methyl-, 2 : 2 - dimethyl -, 2 - acetoxy -, 2 - isobutoxy-4 - phenyl -, 2 - methyl - 2 - (21 - methylalloxy)-methyl -, 2 - methyl - 2 - acetoxy -, 2 : 4 - and 2 : 5 - dimethyl - 2 - carbomethoxy -, 2 - n-butyl -, 2 - carbomethoxy -, 2 - methyl - 2-neopentyl -, 2 : 4 - and 2 : 6 - dimethyl - 2-phenyl -, 2 - isobutoxy - 6 - methyl -, 2 - butoxy 5 - methyl -, 2 - methoxy 5 - methyl -, 2-oxiranyl -, 2 - cyano - 2 - methyl -, 2 - phenyl and 2 - methyl - 2 - phenyl -, 3 : 4 - dihydro-1 : 2-pyran, with, in some cases, by-products resulting from the condensation of the reactants in other than equimolecular proportions.  Lists of additional starting materials and products are given.  Dials and diols.-The Specification as open to inspection under Sect. 91 comprises also the subject-matter of Specification 653,765, and a modification of the processes thereof which consists in using as starting material a 3 : 4-dihydro-1 : 2-pyran containing in the 2-position an organic (hydrocarbon, acyl or thioacyl), radical linked through an element of (Group VI), of the Periodic Table other than oxygen, especially sulphur.  This subject-matter does not appear in the Specification as accepted.