On the mechanism of photoinduced addition of acetonitrile to phosphonium–iodonium ylides1. (7th June 2012)

• Record Type: Journal Article
• Authors: Nekipelova, Tatiana D.; Kuzmin, Vladimir A.; Matveeva, Elena D.; Gleiter, Rolf; Zefirov, Nikolay S.
• Is Part Of: Journal of physical organic chemistry. Volume 26:Number 2(2013:Feb.)
• Page Start: 137
• Page End: 143
• Publication Date: 2012-06-07
• Subjects: cycloaddition reaction -- phosphonium–iodonium ylides -- photolysis -- reactive intermediates -- time‐resolved spectroscopy; Chemistry, Physical organic -- Periodicals; 547.1
• DOI: 10.1002/poc.2972
• Languages: English
• ISSNs: 0894-3230

Abstract

Abstract : Recently, a novel photochemical reaction of pseudocycloaddition of nitriles to mixed phosphonium–iodonium ylides 1 was found. Nitriles R1 CN give corresponding oxazoles (2) with a high yield, with PhI (3) being a leaving group. The mechanism of the photoinduced cycloaddition of acetonitrile to mixed phosphonium–iodonium ylide 1 was studied by steady‐state and time‐resolved methods with resolution from 10 ns to 20 µs. The formation of photolysis products, substituted oxazole 2, and phosphonium salt 4, occurs in parallel reactions. The primary photochemical processes for the formation of 2 and 4 are the heterolytic and homolytic C–I + Ph bond cleavage in the excited singlet state of 1, respectively. Three transient species with lifetimes on microsecond and millisecond time scales were observed. The mechanism of the formation of major and minor products of the photolysis was suggested. Addition of water to the reaction mixture in acetonitrile changes the ratio of the products in favor of the phosphonium salt formation. The effect of water was accounted for by the acid catalysis of the homolytic C–I + Ph bond cleavage and the acceleration of the salt formation. Copyright © 2012 John Wiley & Sons, Ltd. Abstract : The parallel formation of oxazole and phosphonium salt in the photolysis of mixed phosphonium‐iodonium ylide in acetonitrile was shown. Three transient species with lifetimes on microsecond and millisecond time scales were observed and the mechanism of the formation of major and minor products of the photolysis was suggested. Effect of water traces in acetonitrile on the yield of the products was revealed.