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Synlett 2009(1): 129-132  
DOI: 10.1055/s-0028-1087377
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© Georg Thieme Verlag Stuttgart ˙ New York

Silver-Catalyzed C-H Insertion Reactions with Donor-Acceptor Diazoacetates

Carl J. Lovely*, Jaime A. Flores, Xiaofeng Meng, H. V. Rasika Dias*
Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019, USA
Fax: +1(817)2723808; e-Mail: lovely@uta.edu; e-Mail: dias@uta.edu;
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Publication History

Received 5 September 2009
Publication Date:
12 December 2008 (online)

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Abstract

In this paper we describe the first examples of carbene transfer with donor-acceptor diazoacetates and the silver tris(pyrazolyl)borate complex {HB[3,5-(CF3)2Pz]3}Ag(THF). These reactions generally proceed in good yields and exhibit improved selectivities compared to simple diazoacetates.

Key words

organometallic - tris(pyrazolyl)borate - silver - atom transfer - chemoselective

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General Procedure for Catalysis by Carbene-Transfer Reactions with Catalyst {HB[3,5-(CF 3 ) 2 Pz] 3 }Ag(THF): Methyl phenyldiazoacetate or methyl styryldiazoacetate (0.25 mmol) dissolved in the substrate (5 mL) was added by syringe pump over a period of ca. 3 h to a stirred solution of the catalyst (0.005 g, 0.01 mmol) in the substrate (10 mL) in a foil-shielded, round-bottomed flask. The resulting mixture was stirred for 6 h at r.t., concentrated and the residue was purified by flash chromatography on silica gel (2% Et2O-PE for hydrocarbons, 5-20% Et2O-PE for ethers) to yield oily transparent or white solid products. The isolated yields are based on the average of at least two experiments and on the amount of diazoacetate used.

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Methyl 2-Phenyl-3-methylhexanoate: yield: 40.2 mg (73%); diastereoisomer ratio = 1.2:1. ¹H NMR (300 MHz, CDCl3): δ = 7.19-7.36 (m, 10 H, ArH), 3.624 (s, 3 H, OMe), 3.620 (s, 3 H, OMe), 3.24 (d, J = 10.7 Hz, 1 H, CHPh), 3.23 (d, J = 10.3 Hz, 1 H, CHPh), 2.11-2.28 (m, 2 H, CH), 1.01-1.50 (m, 8 H, CH2), 0.98 (d, J = 6.5 Hz, 3 H, Me), 0.89 (t, J = 6.9 Hz, 3 H, Me), 0.73 (t, J = 6.9 Hz, 3 H, Me), 0.65 (d, J = 6.9 Hz, 3 H, Me). ¹³C NMR (125 MHz, CDCl3): δ = 174.54, 174.49, 138.19, 138.14, 128.61, 128.58, 128.42, 128.39, 127.14, 58.8, 55.5, 51.7, 37.6, 36.2, 36.1, 35.6, 19.9, 19.4, 17.8, 16.6, 14.2, 14.0. IR (neat): 3087, 3064, 3029, 2959, 2932, 2873, 1738 cm-¹. HRMS (ESI): m/z [M + H]+ calcd for C14H21O2: 221.1536; found: 221.1537.