Coupling of Fischer carbene complexes with conjugated enediynes featuring radical traps; Novel structure and reactivity features of chromium complexed arene diradical species.
The reaction of Fischer carbene complexes with conjugated enediynes that feature a pendant alkene group has been examined. The reaction proceeds through carbene-alkyne coupling to generate an enyne-ketene intermediate. This intermediate then undergoes Moore cyclization to generate a chromium complexed arene diradical, which then undergoes cyclization with the pendant alkene group. The radical cyclization prefers the 6-endo mode unless radical-stabilizing groups are present to favor the 5-exo mode. The intermediate diradical species were evaluated computationally in both the singlet and triplet configurations. Arene triplet diradicals feature minimal spin density at oxygen and delocalization to chromium. The 6-endo cyclization product was kinetically and thermodynamically favored.
Department of Chemistry and Biochemistry, New Mexico State University, MSC 3C, Las Cruces, New Mexico 88003, USA.
Yi
Y
Zhang
Tareq
T
Irshaidat
Haixia
H
Wang
Kris V
KV
Waynant
Haobin
H
Wang
James W
JW
Herndon