Ethyl bromoacetate → (+/-) ethyl (E)-4-[2-(5,6,7,8-tetrahydro-5,5-dimethyl-8-hydroxy-8-(carbethoxymethyl) naphthalen-2-yl)ethenyl]benzoate

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Reaction Steps

Reaction Scheme 5 discloses another example for the preparation of compounds within the scope of Formula 3. In this example the substituent is introduced to replace the oxo function of tetrahydronaphthalene-2-one after the Z--Y(R2)--A--B group has already been coupled to the tetrahydronaphthalene nucleus. Thus, ethyl (E)-4-[2-(5,6-dihydro-5,5-dimethyl-naphthalen-8(7H)-one-2-yl)ethenyl]benzoate (Compound A2) is reacted with ethyl bromoacetate in the presence of zinc metal in a Reformatsky reaction to provide (±) ethyl (E)-4-[2-(5,6,7,8-tetrahydro-5,5-dimethyl-8-hydroxy-8-(carbethoxymethyl)naphthalen-2-yl)ethenyl]benzoate (Compound A32). Compound A32 is itself within the scope of the present invention, within the scope of Formula 1. Compound A32 is dehydrated, as shown in the example by treatment with (methoxycarbonylsulfamoyl)triethylammonium hydroxide (Burgess reagent) to yield a mixture of ethyl (E)-4-[2-(5,6-dihydro-5,5-dimethyl-8-(carbethoxymethyl)naphthalen-2-yl)ethenyl]benzoate (Compound A33a), and ethyl (E)-4-[2-(5,6-dihydro-5,5-dimethyl-8(7H)-anti (carbethoxymethylidenyl)-naphthalen-2-yl)ethenyl]benzoate (Compound A33b). Compound A33a is within the scope of Formula 6, and Compound A33b is within the scope of Formula 3. ##STR20##

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