AROMATIC SPIRANES .22. PREPARATION OF CYC LOPENTENO-4,5-INDAN-1-ONE AND 2-CARBOMETHOXY-INDANE AND 4-CHLOROMETHYL-INDANE AS SYNTHONES FOR THE SYNTHESES OF ANELLATED 2,2'-SPIROBUNDANONE

The title compounds were prepared as follows: tert.-butyl-indane (10) was formylated to give a 72:28 mixture of the aldehydes 23a and 23b wh ich were submitted to a Knoevenagel-Doebner condensation to afford the cinnamonic acids 24. From the mixture, the pure stereoisomer 24a was obtained by one crystallization in 57% yield. Its methylester 27a coul d be quantitatively dealkylated to the methylester 8 by treatment with AlCl3 in toluene. Cyclization to the indanone 9 was then performed vi a the propionic acid 7 with polyphosphoric acid in 95% yield. From 9 t he carboxymethyl derivative 30 was obtained by treatment with dimethyl carbonate and NaH. The second synthone 4-chlormethylindane (19) was pr epared from the corresponding alcohol 18 (in 82% yield) which in turn could be obtained from methylester 17 by reduction with LiAlH4. The la tter was accessible in 75% yield by dealkylation of ester 13.