Radical rearrangement in the spiro(cyclopropane-1,1'-indan) and 3',4'-dihydrospiro(cyclopropane-1,1'(2H)-naphthalene) systems. An investigation of fast radical clocks

The ring opening rearrangements of cyclopropylcarbinyl radicals incorporated in rigid indanyl and tetrahydronaphthyl frameworks were investigated by the competitive tin hydride method. At 75$\sp\circ$C, the spiro (cyclopropane-1,1$\sp\prime$-indan) -2$\sp\prime$-yl and 3$\sp\prime$,4$\sp\prime$-dihydrospiro (cyclopropane-1,1$\sp\prime$(2$H$)-naphthalene) -2$\sp\prime$-yl radicals undergo ring opening with rate constants of 2.11 $\times$ 10$\sp9$ s$\sp{-1}$ and 2.99 $\times$ 10$\sp9$ s$\sp{-1}$, respectively. The 3$\sp\prime$,3$\sp\prime$-dimethylspiro (cyclopropane-1,1$\sp\prime$-indan) -2$\sp\prime$-yl and 3$\sp\prime$,4$\sp\prime$-dihydro-3$\sp\prime$,3$\sp\prime$-dimethylspiro (cyclopropane-1,1$\sp\prime$(2$H$)-naphthalene) -2$\sp\prime$-yl radicals undergo ring opening with rate constants of 8.53 $\times$ 10$\sp9$ s$\sp{-1}$ and 3.51 $\times$ 10$\sp9$ s$\sp{-1}$, respectively. Dispiro (cyclopropane-1,1$\sp\prime$-indan-3$\sp\prime$,1$\sp{\prime\prime}$-cyclopropane) -2$\sp\prime$-yl radical undergoes ring opening with a rate constant of 5.2 $\times$ 10$\sp8$ x$\sp{-1}$. The rate enhancement observed in the rearrangement of the spiroindanyl and spirotetrahydronaphthyl radicals relative to that of the acyclic cyclopropylmethyl radical ($k\sb{\rm r}$ = 5.21 $\times$ 10$\sp8$ s$\sp{-1}$ at 75$\sp\circ$C) is rationalized in terms of (a) favorable overlap of the reacting orbitals held in a rigid conformation, (b) greater relief of ring strain in the transition state, and (c) stabilization of the developing double bond in the transition state by the adjacent phenyl ring. Semiempirical AM1 and MNDO calculations failed to provide a reasonable correlation with these experimental results. Attempts to evaluate the effect of cyclopropane methyl substituents on the rate of rearrangement of spiroindanyl radicals by an intramolecular competition experiment were unsuccessful, due to the instability of the required radical precursors.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Lemieux, Robert Philippe

Contributors dc:contributor

• Beak, Peter

• Chemistry, Organic

Statement dc:rights

• Copyright 1989 Lemieux, Robert Philippe

Language dc:language

eng

Identifier

AAI9010930
(UMI)AAI9010930

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/19057