Carbon tunneling in the ring expansion of noradamantylchlorocarbene.
Irradiation of 3-(3-noradamantyl)-3-chlorodiazirine produced the corresponding noradamantylchlorocarbene, which could be detected in solution with laser flash photolysis via its pyridinium ylide, and in N2 or Ar matrixes at 9 K with IR and UV/vis spectroscopy. At ambient temperatures, or on irradiation in the cryogenic matrixes, the carbene rearranged to 2-chloro-1-adamantene, which could be trapped in solution and which was characterized by IR and UV/vis at low temperatures. In the dark at 9 K, the carbene also slowly ring-expanded to the chloroadamantene, at a rate ca. 10111 times faster than predicted by its B3LYP-calculated activation barrier. It is proposed that the low-temperature rearrangement occurs through carbon quantum mechanical tunneling.
Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, NJ 08903, USA. moss@rutchem.rutgers.edu
Robert A
RA
Moss
Ronald R
RR
Sauers
Robert S
RS
Sheridan
Jingzhi
J
Tian
Peter S
PS
Zuev