Aromatische Spirane, 22. Mitt.: Darstellung von Cyclopenteno-4,5-indan-1-on und 2-Carboxymethyl-bzw. 4-Chlormethyl-indan als Synthone für Synthesen von anellierten 2,2′-Spirobiindanonen

Summary The title compounds were prepared as follows:tert.-butyl-indane (10) was formylated to give a 72:28 mixture of the aldehydes23a and23b which were submitted to aKnoevenagel-Doebner condensation to afford the cinnamonic acids24. From the mixture, the pure stereoisomer24a was obtained by one crystallization in 57% yield. Its methylester27a could be quantitatively dealkylated to the methylester8 by treatment with AlCl₃ in toluene. Cyclization to the indanone9 was then performedvia the propionic acid7 with polyphosphoric acid in 95% yield. From9 the carboxymethyl derivative30 was obtained by treatment with dimethylcarbonate and NaH. The second synthone 4-chlormethyl-indane (19) was prepared from the corresponding alcohol18 (in 82% yield) which in turn could be obtained from methylester17 by reduction with LiAlH₄. The latter was accessible in 75% yield by dealkylation of ester13.

Herrn Prof. Dr.K. Kratzl mit besten Wünschen zum 80. Geburtstag gewidmet