- In situ generation of nucleophilic allenes by the gold-catalyzed rearrangement of propargylic esters for the highly diastereoselective formation of intermolecular C(sp3)-C(sp2) bonds
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New perspectives, in particular for the synthesis of isochromane derivatives (see scheme), are provided by the title reaction. Excellent diastereoselectivites are achieved in this reaction which proceeds through a gold-catalyzed 1,3-acyloxy migration. In some cases exclusively the Z isomer is detected. Copyright
- Yu, Yang,Yang, Weibo,Rominger, Frank,Hashmi, A. Stephen K.
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supporting information
p. 7586 - 7589
(2013/07/26)
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- Copper-catalyzed enantioselective additions to oxocarbenium ions: Alkynylation of isochroman acetals
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We have developed an enantioselective, copper(I)-catalyzed addition of terminal alkynes to racemic isochroman acetals. This method is one of the first transition-metal-catalyzed approaches to enantioselective additions to prochiral oxocarbenium ions. In this reaction, TMSOTf is used to form the oxocarbenium ion in situ under conditions compatible with simultaneous formation of the chiral copper acetylide. By using a bis(oxazoline) ligand, good yields and enantioselectivities are observed for a variety of enantioenriched 1-alkynyl isochromans.
- Maity, Prantik,Srinivas, Harathi D.,Watson, Mary P.
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p. 17142 - 17145
(2011/12/13)
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- Fluoro- or trifluoromethyl-substituted benzyl and phenethyl alcohols: Substrates for metal-mediated site-selective functionalization
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It was possible to functionalize the three fluorobenzyl alcohols and the three 2-(fluorophenyl)ethanols by metalation and subsequent carboxylation, the prototype electrophilic trapping reaction. Triisopropylsilyl (TIPS) outperformed methoxymethyl (MOM) as an O-protective group making seven new fluorobenzoic acids accessible in 63% average yield. Moreover, the TIPS group tolerates weakly basic and acidic media and, therefore, may facilitate further structural elaboration. The unprotected alcohols reacted more sluggishly and were unable to provide two of the targeted products (acids 1 and 2). The yield averaged only 46% in the five other cases (acids 3-7). The direct metalation of fluorinated benzyl and phenethyl alcohols remains nevertheless an attractive option because of its operational simplicity. All three (trifluoromethyl)benzyl alcohols and two of the three (trifluoromethyl)phenethyl alcohol isomers were successfully submitted to the metalation/functionalization sequence. These five starting materials gave rise to a total of nine new benzoic acids or lactones (compounds 8-14 and 17-18). Despite the poor yields (31% on average), the organometallic methods employed are, in general, extremely selective, economical and easy to perform. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Marzi, Elena,Spitaleri, Andrea,Mongin, Florence,Schlosser, Manfred
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p. 2508 - 2517
(2007/10/03)
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