Cross-Coupling Transition-Metal-Free Cross-Dehydrogenative Coupling of Ethyl Arylacetates with Benzoic/Cinnamic Acids: A Practical Synthesis of a-Acyloxy Esters Anup Kumar Sharma, Promod Kumar, Ramesh Kumar Vishwakarma, and Krishna Nand Singh* [a] Abstract: An efficient cross-dehydrogenative coupling of benzylic C(sp 3 ) ÀH of ethyl arylacetates with benzoic/cin- namic acids has been developed to afford a-acyloxy esters in reasonably high yields under environmentally benign conditions. Cross-dehydrogenative coupling (CDC) reactions have taken a central place in current day organic synthesis due to its advan- tages to construct carbon-carbon/carbon-heteroatom bonds. a-Acyloxy ketones and esters constitute the vital building block of a wide range of natural products and pharmaceuti- cals. [1] a-Acyloxy esters can also be selectively hydrolyzed to the corresponding a-hydroxy esters having high product value in cosmetic, chemical, food, and pharmaceutical industries. [2, 3] The installation of acyloxy substituent at benzylic position is an enduring goal in organic synthesis, and many reports using benzylic/allylic C(sp 3 ) ÀH and O ÀH bonds involving CDC proto- col have appeared adopting different strategies. [4–6] The selec- tive oxidative cleavage of benzylic C(sp 3 ) ÀH and CDC are espe- cially important for the formation of C ÀO bonds, and have been accomplished using transition metal catalysts such as Cu, Fe, Ru, Rh, Ir, and Pd in combination with different oxidants. [7] Jørgensen et al. have established a general route for the rhodi- um-catalyzed N ÀH and O ÀH insertion of amides and carboxylic acids with a-diazo-b-ketoesters to afford a-amido and a-car- boxylic-b-ketoesters, [8] whereas Feng group has recently illus- trated an enantioselective insertion of a-diazoesters and a-di- azoketones into O ÀH bonds of carboxylic acids by using Rh 2 (OAc) 4 and a chiral guanidine (Scheme 1). [9] Sharma et al. ex- tended the scope of reaction by using a Rh 2 (esp) 2 -catalyzed O ÀH insertion of 3-butynoic acid with diazo methylbenzoylace- tate adopting Conia-ene strategy. [10] The esterification of car- boxylic acids has also been achieved via continuous flow di- azotization of amines, [11] iron-catalyzed intermolecular hydro- thiolation of internal alkynes with thiosalicylic acids, [12] and by catalytic Mitsunobu reaction using recyclable azo reagents. [13] N-Heterocyclic carbene (NHC)-based reactions have also been identified to play an important role in constructing the ben- zoate ester via heteroacylation of carbonyl compounds. [14] A biocatalytic pathway involving Baeyer–Villiger Monooxygenas- es (BVMO) has also been explored for the synthesis of enantio- pure a-acylated hydroxy esters. [15] However, most of the afore- mentioned reactions are metal based and invariably make use of diazo esters in the presence of a rhodium catalyst. As an en- vironmentally benign, inexpensive and practically useful meth- odology, the advancement of transition-metal-free reactions is yet challenging. [16] Thus, new and eco-safe protocols employ- ing readily available starting materials are highly exigent to obtain a-acyloxy esters. In view of the above and as a part of our continued interest on metal-free synthesis, [17] we disclose herein a practical syn- thetic strategy adopting oxidative CDC of benzylic C(sp3) ÀH of ethyl arylacetates with benzoic/cinnamic acids to afford diverse range of a-acyloxy esters in the presence of molecular iodine and K 2 CO 3 in DMSO at 80 8C (Scheme 1). In order to optimize the reaction conditions, a model reac- tion using inexpensive and easily available benzoic acid (1a) and ethyl phenylacetate (2a) was thoroughly investigated by Scheme 1. Previous reports and present strategy. [a] A. K. Sharma, P. Kumar, R. K. Vishwakarma, K. N. Singh Department of Chemistry (Centre of Advanced Study) Institute of Science Banaras Hindu University Varanasi 221005 (India) E-mail : knsingh@bhu.ac.in Supporting information and the ORCID identification number(s) for the au- thor(s) of this article can be found under https://doi.org/10.1002/ ajoc.201800029. Asian J. Org. Chem. 2018, 00,0–0  2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1 && These are not the final page numbers! ÞÞ Communication DOI: 10.1002/ajoc.201800029