4,9(11),17(20)-pregnatriene-3-ones

A process for the preparation of a compound of the formula ##STR31## wherein K is a protective group selected from the group consisting ##STR32## n is 2 or 3, the wavy line means the group may have either isomeric form or is a mixture thereof and R.sub.2 is selected from the group consisting of methyl, phenyl, tolyl and xylyl, comprising reacting a compound of the formula ##STR33## with acetic anhydride in the presence of a strong acid, then with an acid hydrolysis agent to obtain a compound of the formula ##STR34## selectively blocking the 3-oxo function with a diol, a thiol or a dithiol of the formula HO--(CH.sub.2).sub.n --OH, HO--(CH.sub.2).sub.n --SH or HS--(CH.sub.2).sub.n --SH,

• wherein n is defined as above to obtain a compound of the formula ##STR35## wherein K is defined as above, reacting the latter with a compound of the formula
• Hal.sub.3 C--CO.sub.2 R
• wherein Hal is chlorine or bromine and R is selected from the group consisting of alkyl of 1 to 6 carbon atoms, aralkyl or 7 to 15 carbon atoms and a silylated group, in the presence of zinc and a Lewis acid, to obtain a compound of the formula ##STR36## reacting the latter in the presence of a base with an alkali metal sulfinate of the formula
• R.sub.2 SO.sub.2 Q
• wherein R.sub.2 is defined as above and Q is an alkali metal, to obtain a compound of the formula ##STR37## in which R, R.sub.2 and K are defined as above, reacting the latter with a halogenation agent in the presence of a base, saponifying and decarboxylating the product to obtain a compound of the formula ##STR38## in which Hal.sub.1 is halogen, reacting the latter with formaldehyde in the presence of a base to obtain the compound of formula XI.