Zirconocene-mediated cyclization of alkynyl-diborylmethanes to 1,3-diborolanes

Article abstract of DOI:10.1021/om00031a009

The carbon-carbon triple bond in bis[(dialkylamino)(phenylethynyl)boryl]methanes 2a,b can be easily cyclized using zirconocene to give derivatives 3a,b of the new pentalene-like 6,8-dibora-3-zirconabicyclo[3.3.0]octa-1,4-diene, containing a zirconacyclopentadiene ring attached to a 1,3-diboracyclopentane unit. These heterocycles are characterized by NMR methods and by an X-ray structure determination of 3b. Compound 3b crystallizes from pentane in the monoclinic space group C2/c with a = 23.11(2) ?, b - 8.123(1) ?, c = 40.08(3) ?, β = 97.63(6)° , V = 7458(8) ?³, and ρ(calc) = 1.175 Mg/m³ for M = 659.7 g/mol and Z = 8.