Acetylenes disubstituted with a phenyl group and a 2-substituted chromanyl, thiochromanyl or 1,2,3,4-tetrahydroquinolinyl group having retinoid-like activity

A process for synthesizing a compound of the formula (i) ##STR11## where X is S or O;

• R.sub.1, R.sub.2 and R.sub.3 are independently hydrogen or lower alkyl;
• R.sub.4 is lower alkyl;
• R.sub.6 is hydrogen, lower alkyl, lower alkenyl or lower cycloalkyl having 1 to 6 carbons or halogen;
• n is an integer from 0 to 5;
• B is hydrogen, COOH or a pharmaceutically acceptable salt, ester or amide thereof, --CH.sub.2 OH or an ether or ester derivative thereof, or CHO or an acetal derivative thereof, or --COR" or a ketal derivative thereof where R" is an alkyl, cycloalkyl or alkenyl group containing 1 to 5 carbons, the process comprising the steps of:
• reacting a compound of formula (ii) ##STR12## where R.sub.1, R.sub.2 and R.sub.3 are defined as above, and Y is halogen when X is S and Y is hydrogen when X is O, with a Grignard reagent having the formula R.sub.4 --Mg--X' where X' is halogen, to obtain a compound of formula (iii) ##STR13## where R.sub.1, R.sub.2, R.sub.3, R.sub.4, X and Y are defined as above;
• converting the compound of formula (iii) to a compound of formula (iv) ##STR14## where R.sub.1, R.sub.2, R.sub.3, R.sub.4 X and Y are defined as above, said step of converting including an elimination reaction;
• saturating the compound of formula (iv) to provide a compound to formula (v) ##STR15## where R.sub.1, R.sub.2, R.sub.3 R.sub.4 X and Y are defined as above;
• converting the compound of formula (v) into the compound of formula (i), said steps of converting (v) into (i) when X is S including steps of reacting the compound of formula (v) with a trialkylsilylacetylene and thereafter removing the trialkylsilyl group from the product of that reaction under basic conditions to obtain the compound of formula (vi), when X is O said step of converting including optionally cyclizing the ring-open form of the hemiacetal, and steps of reacting the compound of formula (v) with an acetylating agent under Friedel Crafts conditions, and thereafter reacting the product of that reaction with strong base to obtain the compound of formula (vi), said step of converting further including a step of reacting a compound of formula (vi) ##STR16## where R.sub.1, R.sub.2, R.sub.3, R.sub.4 and X are defined as above, with a compound of formula (vii) ##STR17## where X' is halogen, and R.sub.6, B and n are defined as above.