Synthese von 6,6‐Dimethylfulven‐2‐carbonsäure‐methylester und ‐2,3‐dicarbonsäure‐dimethylester sowie deren Umsetzung zu 2,3,5,6‐substituierten Nordbornadienen

Synthesis of Methyl 6,6‐Dimethylfulvene‐2‐carboxylate and Dimethyl 6,6‐Dimethylfulvene‐2,3‐dicarboxylate as well as their Reaction to 2,3,5,6‐Substituted Norbornadienes Fulvenes 5 and 6 were synthesized by Diels‐Alder reaction of 6,6‐dimethylfulvene with methyl prop‐2‐ynoate and dimethyl but‐2‐ynedioate, catalytic reduction of the unsubstituted norbornadiene double bond, and a subsequent retro Diels‐Alder reaction under flash vacuum pyrolysis conditions, 5 and 6 are used as the diene component in synthesizing 2,5‐, 2,3,5‐, and 2,3,5,6‐substituted norbornadienes 7–9 by Diels‐Alder reaction with electron‐deficient alkynes.