Substituent dependent cyclization reactions of 1,1'‐bis(alkynyl) ferrocenes with the (C6F5)BH2·SMe2hydroboration reagent

The reaction of 1,1'-bis(tert-butylethynyl)ferrocene (4 a) with the (C6F5)BH2 . SMe2 reagent results in two-fold hydroboration to give the boron containing [3]ferrocenophane 5. It reacts with xylylisocyanide by insertion into the boron-carbon bond to give the ring enlarged boron containing [4]ferrocenophane derivative 8. 1,1'-Bis(trimethylsilylethynyl)ferrocene (4 b) undergoes the hydroboration reaction with (C6F5)BH2 with inverted regioselectivity. This results in the formation of the 16-membered dimeric bis-boron containing macrocyclic bridged bis-ferrocene system 10.