1282537-48-7Relevant academic research and scientific papers
2-Diazo-1-(4-hydroxyphenyl)ethanone: A versatile photochemical and synthetic reagent
Senadheera, Sanjeewa N.,Evans, Anthony S.,Toscano, John P.,Givens, Richard S.
, p. 324 - 341 (2014/02/14)
α-Diazo arylketones are well-known substrates for Wolff rearrangement to phenylacetic acids through a ketene intermediate by either thermal or photochemical activation. Likewise, α-substituted p-hydroxyphenacyl (pHP) esters are substrates for photo-Favorskii rearrangements to phenylacetic acids by a different pathway that purportedly involves a cyclopropanone intermediate. In this paper, we show that the photolysis of a series of α-diazo-p- hydroxyacetophenones and p-hydroxyphenacyl (pHP) α-esters both generate the identical rearranged phenylacetates as major products. Since α-diazo-p-hydroxyacetophenone (1a, pHP N2) contains all the necessary functionalities for either Wolff or Favorskii rearrangement, we were prompted to probe this intriguing mechanistic dichotomy under conditions favorable to the photo-Favorskii rearrangement, i.e., photolysis in hydroxylic media. An investigation of the mechanism for conversion of 1a to p-hydroxyphenyl acetic acid (4a) using time-resolved infrared (TRIR) spectroscopy clearly demonstrates the formation of a ketene intermediate that is subsequently trapped by solvent or nucleophiles. The photoreaction of 1a is quenched by oxygen and sensitized by triplet sensitizers and the quantum yields for 1a-c range from 0.19 to a robust 0.25. The lifetime of the triplet, determined by Stern-Volmer quenching, is 31 ns with a rate for appearance of 4a of k = 7.1 × 10 6 s-1 in aq. acetonitrile (1:1 v:v). These studies establish that the primary rearrangement pathway for 1a involves ketene formation in accordance with the photo-Wolff rearrangement. Furthermore we have also demonstrated the synthetic utility of 1a as an esterification and etherification reagent with a variety of substituted α-diazo-p- hydroxyacetophenones, using them as synthons for efficiently coupling it to acids and phenols to produce pHP protect substrates. The Royal Society of Chemistry and Owner Societies.
Gas-phase fragmentation of deprotonated p-hydroxyphenacyl derivatives
Remes, Marek,Roithova, Jana,Schroeder, Detlef,Cope, Elizabeth D.,Perera, Chamani,Senadheera, Sanjeewa N.,Stensrud, Kenneth,Ma, Chi-Cheng,Givens, Richard S.
supporting information; experimental part, p. 2180 - 2186 (2011/05/28)
Electrospray ionization of methanolic solutions of p-hydroxyphenacyl derivatives HO-C6H4-C(O)-CH2-X (X = leaving group) provides abundant signals for the deprotonated species which are assigned to the corresponding phenolate anions -O-C6H 4-C(O)-CH2-X. Upon collisional activation in the gas phase, these anions inter alia undergo loss of a neutral "C 8H6O2" species concomitant with formation of the corresponding anions X-. The energies required for the loss of the neutral roughly correlate with the gas phase acidities of the conjugate acids (HX). Extensive theoretical studies performed for X = CF3COO in order to reveal the energetically most favorable pathway for the formation of neutral "C8H6O2" suggest three different routes of similar energy demands, involving a spirocyclopropanone, epoxide formation, and a diradical, respectively.
