Chemoselective Bromodeboronation of Organotrifluoroborates Using Tetrabutylammonium Tribromide: Application in (Z)-Dibromoalkene Syntheses (original) (raw)
Synthesis and Minisci Reactions of Organotrifluoroborato Building Blocks
The Journal of Organic Chemistry, 2013
Copper-catalyzed borylation of a variety of organic halides with bis(pinacolato)diboron allows the preparation of diverse potassium organotrifluoroborates. The reactions are mild and general, providing access to a variety of interesting, boron-containing building blocks, including those containing piperidine, pyrrole, azetidine, tetrahydropyran and oxetane substructures. Representative Minisci reactions are reported for select examples. As a consequence of their successful and, thus, increasing use in a variety of reactions, the demand for new boron-containing building blocks is constantly growing. 1 Among them, organotrifluoroborates have been shown to be a valuable alternative to boronic acids owing to the increased stability conferred by the tetracoordinated boron atom. 2,3 In particular, the efficiency of the organotrifluoroborates in a broad range of reactions has been demonstrated, taking advantage of the reactivity of the boron-carbon bond, as well as reactions where the boron is retained. 4,5 Aliphatic potassium organotrifluoroborates can be easily obtained by simply treating appropriate organoboron precursors with potassium bifluoride (KHF 2) or KF in the presence of tartaric acid. 6 In general, the requisite organoborons can be accessed by different methods: 1) reaction of an organometallic (organomagnesium or organolithium) reagent with an electrophilic boron species BX 3 (X=Cl, F, OR); 7,8 2) hydroboration of alkenes; 9,10 or 3) borylation of alkanes by C-H bond activation. 11,12 Recently, much attention has been placed on the use of nucleophilic boron species and, in preference to the highly reactive boryllithiums or NHC-boranes, 13,14 activation of dibora compounds by a nucleophile was found to be a more efficient and useful synthetic protocol. 15,16 More precisely, copper(I)catalyzed reactions were particularly successful in the case of 1,4-additions to unsaturated carbonyl compounds, 17,18 and after the pioneering work on activated electrophiles by Miyaura, 19 the last year has witnessed the emergence of aliphatic borylation of halogenated substrates. Therefore, primary, secondary, and even tertiary alkylboronates have been prepared by Cu-, 20,21 Ni-, 22,23 or Pd-catalysis, 24 providing access to previously problematic targets. 25 Herein, we report the use of this method for the preparation of a variety of
Organic Letters, 2009
Potassium organoselanyltrifluoroborates have been prepared from the corresponding dihalobenzene compounds in 56-92% yields through a facile one-pot, multicomponent reaction. The microwave-promoted Suzuki-Miyaura cross-coupling reaction of these substrates with various aryl and alkenyl bromides in the presence of 3.0 mol % of Pd(PPh 3 ) 4 and 3.0 equiv of K 2 CO 3 in aqueous 1,4-dioxane at 130°C provided the desired compounds in 54-91% yields.
Synthesis and cross-coupling reactions of tetraalkylammonium organotrifluoroborate salts
Tetrahedron Letters, 2001
Treatment of organoboronic acids with hydrofluoric acid generates an in situ tetracoordinate hydronium organotrifluoroborate species which undergoes counterion exchange with tetra-n-butylammonium hydroxide. The resultant tetraalkylammonium salts are as air and moisture stable as their potassium organotrifluoroborate counterparts with the added advantage of being readily soluble in organic media. They were found to undergo Pd-catalyzed Suzuki-Miyaura cross-couplings with a variety of aryl-and alkenylhalides under mild conditions. Their Pd-catalyzed cross-coupling with acid halides is also possible for the generation of ketones.
Synthesis and Reactivity of Solid-Supported Organotrifluoroborates in Suzuki Cross-Coupling
Organic Letters, 2012
Solid-supported organotrifluoroborates were prepared in high yields by ion exchange with Amberlyst resins. The reactivity of solid supported aryltrifluoroborates was evaluated in Suzuki-Miyaura couplings with numerous aryl bromide partners. Electron rich and electron poor substituents were tolerated on both substrates, providing yields up to 90%. Examples of alkyl-, alkenyl-, alkynyl-and heteroaryltrifluoborates were also successfully cross-coupled to aryl halides.