SHORT COMMUNICATION DOI: 10.1002/ejoc.201000237 Chiral Chalcogen Peptides as Ligands for the Catalytic Enantioselective Aryl Transfer Reaction to Aldehydes Ricardo S. Schwab, [a] Letiere C. Soares, [a] Luciano Dornelles, [a] Oscar E. D. Rodrigues,* [a] Márcio W. Paixão, [b] Marcelo Godoi, [c] and Antonio L. Braga* [c] Keywords: Asymmetric synthesis / Chalcogen peptides / Arylboronic acids / Diarylmethanols / Organozinc reagents / Selenium A new series of chiral chalcogen peptides were synthesized from inexpensive and commercially available starting mate- rials. The synthesized compounds were tested as catalysts in the enantioselective arylation of aldehydes by using aryl- Introduction The addition of organometallic reagents to carbonyl compounds is one of the most important carbon–carbon bond-forming processes in synthetic organic chemistry. [1] The enantioselective nature of this reaction provides par- ticularly useful access to chiral secondary alcohols, which are important building blocks and ubiquitous subunits present in many biologically active compounds as well as in medicinal applications. In this context the asymmetric arylation of aldehydes in the presence of a chiral ligand has received special attention [2] since it affords access to chiral diarylmethanols, [3] which are useful intermediates in the synthesis of bioactive compounds and natural products. [4] The application of boronic acids as a nucleophilic aryl species source, through a boron/zinc [5] exchange, is the most commonly used protocol to afford the respective diaryl- methanols. This method allows the exploitation of a broad range of substituted aryl transfer reagents, since a large number of arylboronic acids are commercially available. Another interesting feature of this reaction is that both enantiomers of a given product can be prepared by using the same chiral ligand, simply with an appropriate choice of the reaction partners: arylboronic acid and aldehyde (Scheme 1). [a] Departamento de Química, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil Fax: +55-55-3220-8998 E-mail: rodriguesoed@gmail.com [b] Departamento de Química, Universidade Federal de São Carlos, 13565-905 São Carlos, SP, Brazil [c] Departamento de Química, Universidade Federal de Santa Catarina, 88040-970 Florianópolis, SC, Brazil E-mail: albraga@qmc.ufsc.br Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/ejoc.201000237. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Eur. J. Org. Chem. 2010, 3574–3578 3574 boronic acids as the aryl source. The desired diarylmethanols were obtained in excellent yields and with enantioselectivi- ties up to 91% ee. Scheme1. Catalytic arylation of aldehydes with arylboronic acids. Despite the potential usefulness of this protocol, the asymmetric version of this addition is a dynamic field. The design of catalysts for the enantioselective addition of or- ganozinc reagents to aldehydes has been the focus of inten- sive research. However, only a few efficient catalysts have been developed for this purpose, and most of them are based on bidentate compounds. Successful results for the synthesis of optically active diarylmethanols have been ob- tained mainly by using chiral β-amino alcohols. [6] Further- more, the efficient application of ligands bearing organo- chalcogen moieties are still rare. Recently, the use of chiral amino sulfides for this purpose has been described, afford- ing the desired product with high yields and selectivities (Figure 1). [7] However, to the best of our knowledge, the application of chiral selenium-based compounds as catalysts for the enantioselective addition of PhZnEt to carbonyl com- pounds is not common, and only the ligand developed by Bolm et al. [8] has been applied for this purpose (Figure 1). In addition, peptide-based ligands offer attractive and practical options in the development of new ligands for