Photochemical Reactions of Alkyl Phenylglyoxylates¹

Abstract

Three new photoproducts, ethyl O-benzoyl mandelate (5a), ethyl O-acetylmandelate (6a), and biphenyl triketone (7a) are isolated and identified in the reactions of ethyl phenylglyoxylate (1a) in benzene. Quantum yields and initial rate constants of product formation are shown to be concentration dependent. For the formation of carbonyl product 3 at lower starting material concentrations (<0.01 M), quantum yields greater than 1 are observed. Variations in the quantum yields as a function of reaction time are due to the accumulation of alpha-hydroxyphenyl ketene (D). The relative reactivities of triplet excited states of phenylglyoxylates 1 and phenyl ketones are compared. A mechanism involving both intramolecular gamma-H abstraction and intermolecular H abstraction, which leads to radical chain reaction, is proposed. Rate constants for intramolecular gamma-H abstraction (k(N)) and intermolecular H abstraction (k(I)) of methyl phenylglyoxylate (1d) are measured.

Controlled Release of Perfumery Aldehydes and Ketones by Norrish Type-II Photofragmentation of -Keto Esters in Undegassed Solution

“…IR (neat): 2932s, 2856m, 1747m, 1727s, 1451m, 1379m, 1311w, 1276m, 1230m, 1183w, 1173w, 1140m, 1118w, 1082m, 1067m, 1050w, 1029w, 997m, 942w, 895w, 837w. 2926m, 2853m, 1743m, 1721s, 1670w, 1449m, 1376m, 1341w, 1331w, 1309w, 1273m, 1267m, 1227m, 1183w, 1139m, 1111w, 1080m, 1063s, 1027w, 993s, 915m, 895w, 830w, 805w, 787w, 739w, 2924s, 2852m, 1745m, 1723s, 1466m, 1450m, 1377w, 1330w, 1310w, 1290w, 1274m, 1229m, 1183w, 1139m, 1117w, 1082m, 1065m, 1028w, 995m, 929w, 895w, 867w, 802w, 785w, 720m, 3089w, 3055w, 3021w, 2953m, 2928m, 2855m, 1723s, 1512m, 1450m, 1410w, 1387w, 1364w, 1310w, 1270m, 1226m, 1183w, 1139m, 1112w, 1079m, 1064m, 998m, 963w, 954w, 919w, 892w, 843w, 800w, (9), 84 (7), 83 (100), 57 (14), 55 (20), 41 (9). 2949m, 2928m, 2854m, 1717s, 1450m, 1387w, 1370m, 1332w, 1311w, 1274m, 1230m, 1181w, 1139m, 1111w, 1081m, 1064m, 1037w, 1027w, 1006w, 995s, 980m, 951m, 912m, 894m, 869w, 844m, 802w, 2924m, 2853m, 1806w, 1719s, 1461w, 1449m, 1376w, 1311w, 1275m, 1254w, 1229m, 1183w, 1139m, 1116w, 1081m, 1064m, 1028w, 996m, 968w, 925w, 894w, 2929s, 2855m, 1800w, 1719s, 1462w, 1448m, 1387w, 1377w, 1364w, 1323w, 1309w, 1274m, 1254w, 1228m, 1182w, 1160w, 1140m, 1108w, 1081m, 1064m, 1047w, 1005w, 995s, 948w, 928w, 906w, 894w, 875w, 830w, 805w, 780w, 745w, 3483w, 2956m, 2869m, 1723s, 1684m, 1469w, 1449m, 1399w, 1372w, 1318w, 1296m, 1254s, 1194m, 1159m, 1140m, 1091s, 1043s, 1029s, 952m, 906m, 858m, 780m, 708w.…”

“…In the case of long-chain alkyl a-keto acids or esters, an intramolecular H shift from the alkyl moiety to the carbonyl O-atom has been observed, yielding an alkene and, after tautomerization, an a-keto acid or ester (Scheme 1) [13]. Intermolecular H abstraction, which has even been observed in apolar, non-H-donating solvents, results in the formation of different dimeric structures [4] [9].…”

“…A large number of protocols for the preparation of a-keto esters have been reported (see, e.g., [18]). Commercially available a-keto acids can directly be esterified with different alcohols in the presence of TsOH under azeotropic removal of water [19], under N,N'-dicyclohexylcarbodiimide (DCC) coupling conditions in the presence of 4-(dimethylamino)pyridine (DMAP) [9] [20] or with pyridine [12] from their corresponding acid chlorides [21]. Thus a-keto esters 1 ± 5 (cf.…”

Design of organic electroluminescent displays with ultraviolet‐shielding filters

“…Some derivatives serve as intermediates in the synthesis of α‐amino acids and are commercially available. Others are accessible by double carbonylations of aryl halides with CO using Pd,12 Co,13 or Cu catalysts,14 by Friedel–Crafts acylations with oxalyl chlorides,15 additions of arylmetal reagents to oxalates,16 or oxidations of acetophenones 17…”

Synthesis of α,β‐Unsaturated Ketones by Pd‐Catalyzed Decarboxylative Allylation of α‐Oxocarboxylates

“…[11] Some derivatives serve as intermediates in the synthesis of a-amino acids and are commercially available. Others are accessible by double carbonylations of aryl halides with CO using Pd, [12] Co, [13] or Cu catalysts, [14] by Friedel-Crafts acylations with oxalyl chlorides, [15] additions of arylmetal reagents to oxalates, [16] or oxidations of acetophenones. [17] We herein report the Pd/phosphine-catalyzed decarboxylative allylation of allyl a-oxocarboxylates as the first example of a decarboxylative allylation involving destabilized carbon nucleophiles (see Scheme 1,bottom).…”