6-Tetralones, general synthesis

A further example is given below illustrating the use of a dibasic anhydride (succinic anhydride) the succinoylation reaction is a valuable one since it leads to aroyl carboxylic acids and ultimately to polynuclear hydrocarbons. This general scheme of synthesis of substituted hydrocarbons through the use of succinic anhydride is sometimes called the Haworth reaction. Thus a-tetralone (see below) may be reduced by the Clemmensen method to tetralin (tetrahydronaphthalene) and the latter converted into naphthalene either catal3d.ically or by means of sulphur or selenium (compare Section, VI,33). 

Besides the general application in synthesis of cycloheptatrienes, different bicyclic products—for example, 0-tetralones and azulenones—can be prepared via the intramolecular Buchner ring expansion. 

This general method has been applied in particular to the case where Rj = CH3 and R2 = CHjCgHj. Vast synthetic possibilities are thus available for the preparation in high yields of indanone and tetralone derivatives disubstituted in the 2 position. These arene complexes (e.g., LXVII) are also of considerable use in annulation reactions (Jaouen and Meyer, 1976) and in the synthesis of spiro compounds (Meyer et al, 1977). 

Syntheses via BCD Intermediates with a Five-Mem-bered Ring D. These syntheses generally start from 6-methoxy-l-tetralone or its 5-methyl derivative, which are used as the BC fragments. All the methods used in Chapter II for the synthesis of estrogenic hormones from 14-oxa compounds are employed for the construction of ring D. It must be mentioned that some of the intermediates illustrated in Schemes 70 and 71 have also been obtained by syntheses of the BD - C type (cf. Section 3 of this chapter). 

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