Production of vitamin K.sub.1 and vitamin K.sub.2

A process for producing a hydro-precursor for vitamin K.sub.1 or vitamin K.sub.2 which comprises reacting (A) 2-methylhydronaphthoquinone-1,4 with (B) a compound selected from the group consisting of phytyl bromide, isophytyl bromide, geranyl bromide, farnesyl bromide, geranylgeranyl bromide and the corresponding chlorides in a reaction system which comprises an emulsion of (1) an aqueous phase comprising an aqueous solution of an alkali based on an alkali metal and (2) an oily phase comprising a hydrophobic organic solvent which is able to at least partially dissolve said hydro-precursor,

• said reaction being carried out in the presence of at least a catalytic quantity of a salt having a quaternary ammonium ion represented by the formula (I) or a tetraalkyl phosphonium ion represented by the formula (II):
• ##STR3## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 each represent an alkyl or aralkyl group containing from 1 to 20 carbon atoms and the sum of the number of carbon atoms in R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is at least 12, the anion of said salt being a halide, hydrogen sulfate, nitrate or acetate,
• said reaction being carried out under conditions which result in production of said hydro-precursor, said hydroprecursor being 2-methylhydronaphthoquinone-1,4 whose 3-position is substituted by phytyl, isophytyl, geranyl, farnesyl or geranylgeranyl.