2 the process for the preparation of 1 alkyl 2 3 4 5 tetrahydro 1 4 benzodiazepines involves reaction of a 4 substituted 2 3 4 5 tetrahyrdro 1 4 benzodiazepine with an aldehyde in the presence of a hydrosilane and lewis acid in a suitable solvent or solvent mixtures the 4 substituted 2 3 4 5 tetrahydro 1 4 benzodiazepine includes 4 acyl and 4 sulfonyl 2 3 4 5 tetrahydro 1 4 benzodiazepines with the latter preferred the aldehyde includes aliphatic and aromatic aldehydes with imidazole4 carboxaldehyde preferred the hydrosilane used in the reaction includes trialkyl and aryl hydrosilanes with hydrotriethylsilane preferred the lewis acid used in the reaction includes protonic acids such as trifluoroacetic acid and trifluoromethanesulfonic acid and non protonic acids such as boron trifluoride with trifluoroacetic acid being the preferred lewis acid suitable solvent s include hydrocarbons halogenated hydrocarbons ethers esters amides and nitriles the preferred solvent is dichloromethane the reaction temperatures range from 110 to 150 u00b0 c with 0 100 u00b0 c preferred the following examples illustrate the invention but should not be interpreted as a limitation thereon to a stirred solution of 3r 3 4 fluorobenzyl 7 cyano 2 3 4 5 tetrahydro 1 4 benzodiazepine 3 6 g in anhydrous methylene chloride 50 ml and diisopropylethylamine 3 5 ml was added phenylsulfonyl chloride 1 5 ml at 0 u00b0 c in.