Esterification polymeric carrier

Double bonds of benzene and related aromatic compounds do not react with diazoalkanes in 1,3-cycloadditions. The corresponding benzo-annellated dihydro-pyrazoles such as (1 a,6a)-6,9,9-trimethyl-7,8-diazabicyclo[4.3.0]nona-2,5,7-triene (6.98, R = H) can be synthesized, however, from methyl cyclohexa-l,4-dienecarboxy-late (6.97, R = H), as shown by Klarner et al. (1990). The reduction of the ester group to a methyl group was carried out with di-isobutylaluminum hydride (DIBAL-H), esterification of the OH group with methanesulfonyl chloride and reduction with lithium triethyl borohydride. The second double bond was introduced by bromina-tion with Br2 on a polymeric carrier after Bongini et al. (1980). Cycloaddition with 2-diazopropane in ether at -- 5 °C and the following steps gave 6.98 in a yield of 58%. 

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