Synthesis and stereochemistry of some 9,10-dihydroanthracenes

The geometry of the 9,10-dihydroanthracene system is discussed, leading to an explanation of the relevance of conformational analysis for 9,10-dihydroanthracene derivatives. Synthetic routes to 9,10-dialkyl- 9,10-dihydroanthracene-9,10-diols are reviewed, indicating any assign­ments of configuration or conformation which have been made for such dials. Products derived by dehydration of these dials are then discussed. The products isolated from the Grignard reactions of ethyl­magnesium bromide, n-propylmagnesium bromide, i-butylmagnesium bromide, isopropylmagnesium chloride, and neopentylmagnesium chloride with anthraquinone are described. In the main, these products are dials of the above type, or substituted anthrones formed by a 1,2-addition of Grignard reagent to one of the carbonyl groups of anthraquinone, or substituted a.nthrones formed by a 1,6-addition of Grignard reagent to anthraquinone. Detailed conformational analysis of the diethyl and di-n-propyl dials is made, and an unsuccessful attempt to elucidate the complete structure of the 1,6-addition products is described. The dehydration of the diethyl and dimethyl diols with acetyl chloride is shown to give 9,10-substituted anthracene derivatives