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Mild and Regioselective Pd(OAc)2-Catalyzed C-H Arylation of Tryptophans by [ArN2]X, Promoted by Tosic Acid.
ACS Catal. 2017 Aug 04; 7(8):5174-5179.AC

Abstract

A regioselective Pd-mediated C-H bond arylation methodology for tryptophans, utilizing stable aryldiazonium salts, affords C2-arylated tryptophan derivatives, in several cases quantitatively. The reactions proceed in air, without base, and at room temperature in EtOAc. The synthetic methodology has been evaluated and compared against other tryptophan derivative arylation methods using the CHEM21 green chemistry toolkit. The behavior of the Pd catalyst species has been probed in preliminary mechanistic studies, which indicate that the reaction is operating homogeneously, although Pd nanoparticles are formed during substrate turnover. The effects of these higher order Pd species on catalysis, under the reaction conditions examined, appear to be minimal: e.g., acting as a Pd reservoir in the latter stages of substrate turnover or as a moribund form (derived from catalyst deactivation). We have determined that TsOH shortens the induction period observed when [ArN2]BF4 salts are employed with Pd(OAc)2. Pd(OTs)2(MeCN)2 was found to be a superior precatalyst (confirmed by kinetic studies) in comparison to Pd(OAc)2.

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Authors+Show Affiliations

Department of Chemistry, University of York, York YO10 5DD, U.K.

Department of Chemistry, University of York, York YO10 5DD, U.K.

Department of Chemistry, University of York, York YO10 5DD, U.K.

Department of Chemistry, University of York, York YO10 5DD, U.K.

Department of Chemistry, University of York, York YO10 5DD, U.K.

Department of Chemistry, University of York, York YO10 5DD, U.K.

Department of Chemistry, University of York, York YO10 5DD, U.K.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

28824821

Citation

Reay, Alan J., et al. "Mild and Regioselective Pd(OAc)2-Catalyzed C-H Arylation of Tryptophans By [ArN2]X, Promoted By Tosic Acid." ACS Catalysis, vol. 7, no. 8, 2017, pp. 5174-5179.

Reay AJ, Hammarback LA, Bray JTW, et al. Mild and Regioselective Pd(OAc)2-Catalyzed C-H Arylation of Tryptophans by [ArN2]X, Promoted by Tosic Acid. ACS Catal. 2017;7(8):5174-5179.

Reay, A. J., Hammarback, L. A., Bray, J. T. W., Sheridan, T., Turnbull, D., Whitwood, A. C., & Fairlamb, I. J. S. (2017). Mild and Regioselective Pd(OAc)2-Catalyzed C-H Arylation of Tryptophans by [ArN2]X, Promoted by Tosic Acid. ACS Catalysis, 7(8), 5174-5179. https://doi.org/10.1021/acscatal.6b03121

Reay AJ, et al. Mild and Regioselective Pd(OAc)2-Catalyzed C-H Arylation of Tryptophans By [ArN2]X, Promoted By Tosic Acid. ACS Catal. 2017 Aug 4;7(8):5174-5179. PubMed PMID: 28824821.

* Article titles in AMA citation format should be in sentence-case

TY - JOUR T1 - Mild and Regioselective Pd(OAc)2-Catalyzed C-H Arylation of Tryptophans by [ArN2]X, Promoted by Tosic Acid. AU - Reay,Alan J, AU - Hammarback,L Anders, AU - Bray,Joshua T W, AU - Sheridan,Thomas, AU - Turnbull,David, AU - Whitwood,Adrian C, AU - Fairlamb,Ian J S, Y1 - 2017/07/10/ PY - 2016/11/02/received PY - 2017/06/10/revised PY - 2017/8/22/entrez PY - 2017/8/22/pubmed PY - 2017/8/22/medline KW - aryldiazonium salt KW - chirality KW - cross-coupling KW - directing group KW - heteroarene KW - palladium KW - regioselectivity SP - 5174 EP - 5179 JF - ACS catalysis JO - ACS Catal VL - 7 IS - 8 N2 - A regioselective Pd-mediated C-H bond arylation methodology for tryptophans, utilizing stable aryldiazonium salts, affords C2-arylated tryptophan derivatives, in several cases quantitatively. The reactions proceed in air, without base, and at room temperature in EtOAc. The synthetic methodology has been evaluated and compared against other tryptophan derivative arylation methods using the CHEM21 green chemistry toolkit. The behavior of the Pd catalyst species has been probed in preliminary mechanistic studies, which indicate that the reaction is operating homogeneously, although Pd nanoparticles are formed during substrate turnover. The effects of these higher order Pd species on catalysis, under the reaction conditions examined, appear to be minimal: e.g., acting as a Pd reservoir in the latter stages of substrate turnover or as a moribund form (derived from catalyst deactivation). We have determined that TsOH shortens the induction period observed when [ArN2]BF4 salts are employed with Pd(OAc)2. Pd(OTs)2(MeCN)2 was found to be a superior precatalyst (confirmed by kinetic studies) in comparison to Pd(OAc)2. SN - 2155-5435 UR - https://www.unboundmedicine.com/medline/citation/28824821/Mild_and_Regioselective_Pd_OAc_2_Catalyzed_C_H_Arylation_of_Tryptophans_by_[ArN2]X_Promoted_by_Tosic_Acid_ L2 - http://dx.doi.org/10.1021/acscatal.6b03121 DB - PRIME DP - Unbound Medicine ER -