Organic Lab Reactions 26

Organic Lab Reactions 26 - OTHER METHODS OF SYNTHESIS OF...

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Unformatted text preview: OTHER METHODS OF SYNTHESIS OF ALLYLPHENOLS 21 The condensation of allylic alcohols with phenolic compounds in the presence of an acid catalyst yields allylphenols. This reaction was used 86 in a synthesis of vitamin K (LXXVo) by condensing phytol with 2-methyl-l,4-naphthohydroquinone in dioxane with oxalic or trichloro- acetic acid as catalyst; the hydroquinone first formed was oxidized to CH 8 H 2 CH=C(CH 3 )CH 2 Ci6H3i LXXVo LXXVi the quinone LXXVa. An interesting side reaction here was the forma- tion of the isomeric diketone LXXVb. 87 This method of synthesis seems to be superior to the C-alkylation by the use of phytyl bromide and the sodium salt of the hydroquinone, 86 and to the condensation of phytyl bromide with the hydroquinone with zinc as a catalyst. 88 Frequently, however, condensation of an allylic alcohol with a phenol leads to a chroman derivative, as in the synthesis of vitamin E (LXXVII) from phytot and trimethylhydroquinone....
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