agent as the 70 solution and employ a solvent having a freezing point such that it will be liquid at the selected reaction temperature usually the solvent has a freezing point or freezing range below about 40 u00b0 c and preferably below about 60 u00b0 c suitable solvents include ethers particularly alkyl ethers either open chain or cyclic such as ethylene glycol dimethyl ether tert butyl ethyl ether butyl methyl ether cyclohexyl methyl ether di n propyl ether diethyl ether dimethyl ether and tetrahydrofuran preferably tetrahydrofuran is employed with the benzene or toluene solution of the reducing agent the quantity of solvent is not critical and is used in amounts to provide a fluid reaction mixture which is readily determined empirically after the reduction is complete any excess of vitride remaining is decomposed by adding chilled aqueous 20 sulfuric acid to the reaction mixture and permitting the temperature to rise slightly i e about 10 to 20 degrees the intermediate obtained whether a cyclic hemi acetal or a linear dihydrate is isolated and dried before dehydration to the dialdehyde when the reduction affords a cyclic hemi acetal intermediate the dialdehyde may be obtained by dissolving the compound in a mixture of ethanol 15 hcl refluxing for about one hour evaporating to dryness under reduced pressure azeotroping with benzene to effect drying and then treating the residue with a dehydrating agent in an inert anhydrous organic solvent for example the dehydration reaction is conveniently carried out using phosphorus pentoxide as the preferred dehydrating agent in an amount of 2 to 3 equivalents per equivalent of intermediate in an inert anhydrous organic solvent having a boiling higher than the product such that substantially all of.