Amino substituted bisketenes: generation, structure, and reactivity.
Hitherto unknown diamino-substituted bisketenes with both free (14) and tethered (16) amino substituents have been generated by using laser flash photolysis for ring opening of the corresponding cyclobutenediones. The time-resolved kinetics of ring closure of the amino bisketenes back to the cyclobutenediones were measured by IR or UV spectroscopy, and give first-order rate constants which vary by a factor of 7.5x10(4), and the bis(Me2N) bisketene 14 is the most reactive in ring closure that has been reported. Rate constants for ring closure of these and previously observed bisketenes vary by a factor of 10(13). The dialkylamino bisketenes 16 (R=Me, n-Bu) with tethered substituents and restricted geometries are less reactive than the bis(Me2N) bisketene 14 by factors of 1700 and 540, respectively. Computational results obtained with DFT methods suggest angle strain in the tethered cyclobutenediones 15 inhibits facile cyclization of bisketenes 16.
Fu
Nanyan
N
Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
Allen
Annette D
AD
Kobayashi
Shinjiro
S
Tidwell
Thomas T
TT
Vukovic
Sinisa
S
Arumugam
Selvananthan
S
Popik
Vladimir V
VV
Mishima
Masaaki
M
D000588:Amines / Q000737:chemistry*; D002073:Butanes / Q000737:chemistry*; D003500:Cyclization / Q000528:radiation effects; D003503:Cyclobutanes / Q000528:radiation effects*; D007659:Ketones / Q000737:chemistry* / Q000528:radiation effects; D007700:Kinetics; D008968:Molecular Conformation; D010782:Photolysis; D013057:Spectrum Analysis
D000588:Amines; D002073:Butanes; D003503:Cyclobutanes; D007659:Ketones