Kinetic stabilization and reactivity of π single-bonded species have been investigated in detail by generating a series of singlet 2,2-dialkoxy-1,3-diphenyloctahydropentalene-1,3-diyls (DRs). The lifetime at 293 K in benzene was found to increase when the carbon chain length of the alkoxy groups was increased; 292 ns (DRb; OR=OR′=OCH3) <880 ns (DRc; OR=OR′=OC2H5) <1899 ns (DRd; OR=OR′=OC3H7) ≈2292 ns (DRe; OR=OR′=OC6H13) ≈2146 ns (DRf; OR=OR′=OC10H21). DRh (OR=OC3H7, OR′=OCH3; 935 ns) with the mixed-acetal moiety is a longer-lived species than another diastereomer DRg (OR=OCH3, OR′=OC3H7; 516 ns). Activation parameters determined for the first-order decay process reveal that the enthalpy factor plays a crucial role in determining the energy barrier of the ring-closing reaction, that is, from the π-bonding to the σ-bonding compounds. Computational studies using density functional theory provided more insight into the structures of the singlet species with π single-bonded character and the transition states for the ring-closing reaction, thereby clarifying the role of the alkoxy group on the lifetime and the stereoselectivity of the ring-closing reaction.
If you can't find a tool you're looking for, please click the link at the top of the page to "Go to old article view". Alternatively, view our Knowledge Base articles for additional help. Your feedback is important to us, so please let us know if you have comments or ideas for improvement.