Furyl hydroperoxides

The Mo(CO)6-TBHP system promoted autoxidation of 5-alkylidenene-4,5-dihydrofurans (168) under mild conditions, allowing the preparation of primary, secondary and tertiary furyl hydroperoxides. A radical mechanism has been proposed and was supported by the experimental data. 

In 2001, Scettri and coworkers could show that titanium-catalyzed asymmetric sulfoxidation with a tertiary furyl hydroperoxide 188a can be achieved under catalytic conditions by a modification of Uemura s approach employing (R)-BINOL as chiral ligand (equation 57). Under these conditions sulfoxides could be isolated in medium to good... 

SCHEME 113. Ti/DET-catalyzed asymmetric sulfoxidation using a steroidal furyl hydroperoxide 191a as oxidant... 

The last VCD example by Lattanzi et al. describes the use of VCD and DFT calculations to assign the absolute configuration of a recently prepared (15,4/ )-norcamphor-derived furyl hydroperoxide, (+)-8, introduced as a less hindered and more reactive stereoselective oxidant in organic synthesis. During the preparation of 8 through the hydroperoxidation of an alcohol precursor via nucleophilic substitution, it is expected that epimerization will occur at carbon 2 of the bicyclic framework leading to the formation of either exo- or endo-8 (Figure 53.25). Therefore, the... 

Lattanzi A, Scettri A, Zanasi R, Devlin FJ, Stephens PJ. Absolute configuration assignment of norcamphor-derived furyl hydroperoxide using density functional theory calculations of optical rotation and vibrational circular dichroism. J. Org. Chem. 2010 75(7) 2179-2188. 

Furfural (furfuraldehyde) is a very inexpensive starting material obtained from the left-overs of agriculture (acidic distillation of straw and brans) [506]. It adds MeMgCl giving racemic l-(2-furyl)ethanol (( )-396) which has been resolved easily using either enzymatic methods [507,508,509] or metal-catalyzed kinetic resolution [510,511]. For instance, the reaction ( )-396 with f-butyl hydroperoxide in the presence of catalytic amounts of Ti(0-i-Pr)4 and L-(+)-di-isopropyl tartrate (l-(-i-)-DIPT) gives a mixture of optically active (+)-396 andpyranone 397. These compounds are separated readily and isolated in 32 and 53% yield, respectively (O Scheme 100) [512,513]. 

The Achmatowicz reaction is based on the foregoing oxidative cleavage of the fiiran ring in furyl alcohols 49, whose oxidation is preferentially performed with tert-butyl hydroperoxide or MCPBA. The primarily formed l-hydroxy-2,5-dicarbonyl compounds 50 immediately cyclize to the corresponding pyranones 51 by intramolecular hemiacetal... 

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