94088-21-8Relevant articles and documents
Selective generation of free radicals from epoxides using a transition-metal radical. A powerful new tool for organic synthesis
RajanBabu,Nugent, William A.
, p. 986 - 997 (2007/10/02)
Bis(cyclopentadienyl)titanium(III) chloride reacts with epoxides by initial C-O homolysis. The regiochemistry of the opening is determined by the relative stabilities of the radicals. Depending on the reaction partners, these radicals undergo intramolecular (hex-5-enyl cyclization) or intermolecular additions to olefins. The resultant radicals are efficiently scavenged by a second equivalent of Ti(III) to afford the corresponding Ti(IV) derivative. Treatment of this intermediate with electrophiles such as H+ or halogens provides a route to functionalized cyclopentanes and other useful products. The radical initially formed from an epoxide can also be trapped by H-atom donors such as 1,4-cyclohexadiene or tert-butyl thiol, resulting in an overall reduction of the epoxide. In the absence of a H-atom donor or an olefin, this radical is trapped by Ti(III), resulting in a β-oxido-Ti organometallic species which undergoes facile elimination to give an olefin. The reaction conditions are remarkably mild and are applicable to very sensitive substrates.
Synthetic and Stereochemical Studies of the Octahydro-1-benzopyran System
Griffiths, D. Vaughan,Wilcox, Geoffrey
, p. 431 - 436 (2007/10/02)
The cis and trans isomers of the octahydro-1-benzopyran system have been synthesised and their conformations studied by low-temperature (13)C and highfield (1)H n.m.r. spectroscopy.The position of the conformational equilibrium in the cis isomer at -70 deg C in CDCl3-CFCl3 (50:50) has been determined as approximately 99.5:0.5 (ΔG0 -8.9 kJ mol-1) in favour of the conformation having the oxygen axially disposed towards the cyclohexane ring.
