Naphthyl boronic acid

Rh(COD)Cl]2/dppb as the catalytic complex, with phenyl and 2-naphthyl boronic acid as arylating reagents in basic aqueous dioxane, enone-ketone 229 was cy-clized in moderate to good yields. 

Phosphoric acids 3 bearing different aromatic substituents at the 3,3 -positions can be synthesized in a few steps starting from commercially available BINOL (6) (Scheme 3). The key step involves a palladium-catalyzed cross-coupling of boronic acid 7 and the respective aryl halide. Both the electronic and steric properties of potential catalyst 3 can be tuned by a proper choice of the substituents at the 3,3 -positions. Besides a simple phenyl group, Akiyama et al. introduced monosubsti-tuted phenyl derivatives as well as a mesityl group, whereas Terada and coworkers focused on substituents such as biphenyl or 4-(2-naphthyl)-phenyl. 

Cytoxazone is a novel cytokine modulator. The total synthesis of this natural product and its enantiomer was accomplished by S. Sugiyama. The 3-amino-1,2-propanediol moiety was synthesized by a Petasis boronic acid-Mannich reaction between DL-glyceraldehyde, (R)-1-(1-naphthyl)ethylamine and 4-methoxyphenylboronic acid to provide a 1 1 mixture of the diastereomeric products. The diastereomers could be separated at a later stage in the synthesis and transformed into (-)- and (+)-cytoxazone. 

Figure 11.1.25 shows data from a microdroplet liquid-liquid voltammetry experiment in which lactate anions A are transferred from the aqueous phase into the organic microdroplet phase (here composed of the organic solvent 4-(3-phenylpropyl)-pyridine or PPP containing a Mn(III/II) redox system and naphthyl-2-boronic acid B [120]). Schematically, the oxidation of each metal complex Mn(II)TPP (with TPP = tetraphenylporphyrinato) is generating a positive charge within the microdroplet and this is coupled to the reversible transfer of the anion A ... 

Fig. II.1.25 (a) Schematic representation of the transfer of anion from the aqueous into the organic phase upon oxidation of Mn(II)TPP to Mn(III)TPP . (b) In the presence of the boronic acid B as a facilitator the tiansfer of the anion A leads to the formation of the complex AB in the oiganic phase, (c) Cyclic voltammograms [120] (scan rate 10 mVs ) for the oxidation and le-ieduction of 75 mM Mn(II)TPP dissolved in PPP (4-(3-phenylpropyl)-pyridine, 75 nL) and immobilised in the form of microdroplets onto a 4.9-mm diameter graphite electrode immersed in aqueous 0.1 M sodium lactate pH = 7.34. The presence of (i) 0 and (ii) 973 mM naphthyl-2-borDnic add is shown to cause a negative shift in the voltammetric response, (d) Plot of the midpoint potential versus the natural logarithm of the naphthyl-2-boronic add concentration in the microdroplets. Lines indicate calculated data [120] for reversible lactate-4)oronic add complex formation for three equilibrium constants...

The three basic steps in the palladium-catalysed Suzuki-Miyaura reaction involve oxidative addition, transmetalation, and reductive elimination. A systematic study of the transmetalation step has found that the major process involves the reaction of a palladium hydroxo complex with boronic acid, path B in Scheme 3, rather than the reaction of a palladium halide complex with trihydroxyborate, path A. A kinetic study using electrochemical techniques of Suzuki—Miyaura reactions in DMF has also emphasized the important function of hydroxide ions. These ions favour reaction by forming the reactive palladium hydroxo complex and also by promoting reductive elimination. However, their role is a compromise as they disfavour reaction by forming of unreactive anionic trihydroxyborate. A method for coupling arylboronic acids with aryl sulfonates or halides has been developed using a nickel-naphthyl complex as a pre-catalyst. It works at room temperature in toluene solvent in the presence of water and potassium carbonate. ... 

Suzuki coupling of optically active (S)-binaphthyl bromide 2 with (S)-binaphthyl-boronic acid 3 produced a diastereomeric mixture (1 1 mixture) of tetrabutoxyquater-naphthyl 4, The C-1 and C-1 axis of the compound has an unusually high rotational barrier (Equation 8) [9]. 

Reagents and conditions naphthyl bromide (1.0 equiv), boronic acid (1.2 equiv), Pd cat., K2CO3 (2.4 equiv), toluene, 24 h Reaction stopped after 8 h... 

Chiral imines derived from 1-phenylethanone and (I. Sj-exo-l, 7,7-trimethyIbicyclo-[2.2.1]heptan-2-amine [(S)-isobornylamine], (.S>1-phenylethanamine or (R)-l-(1-naphthyl) ethanamine are transformed into the corresponding (vinylamino)dichloroboranes (e.g., 3) by treatment with trichloroborane and triethylamine in dichloromethane. Reaction of the chiral boron azaenolates with aromatic aldehydes at 25 "C, and subsequent acidic hydrolysis, furnishes aldol adducts with enantiomeric excesses in the range of 2.5 to 47.7%. Significantly lower asymmetric inductions are obtained from additions of the corresponding lithium and magnesium azaenolates. Best results arc achieved using (.S )-isobornylamine as the chiral auxiliary 3. 

An example of an alcohol that can undergo rapid skeletal rearrangement is 3,3-dimethyl-2-phenyl-2-butanol (Eq. 29). Attempts to reduce this alcohol in dichloromethane solution with l-naphthyl(phenyl)methylsilane yield only a mixture of the rearranged elimination products 3,3-dimethyl-2-phenyl-l-butene and 2,3-dimethy 1-3-phenyl-1 -butene when trifluoroacetic acid or methanesulfonic acid is used. Use of a 1 1 triflic acid/triflic anhydride mixture with a 50 mol% excess of the silane gives good yields of the unrearranged reduction product 3,3-dimethyl-2-phenylbutane, but also causes extensive decomposition of the silane.126 In contrast, introduction of boron trifluoride gas into a dichloromethane solution of the alcohol and a 10 mol% excess of the silane... 

Using 9.2 mmoles each of o-cresol and a-naphthyl isocyanate in 3.00 ml of purified ligroin, the effect of catalysts was tested. The sealed tubes were heated in a 65°C bath and after a definite time the solid urethane derivative was isolated, washed, dried, and weighed. The results (see Fig. 1) show that tri-ethylamine is the most effective amine, boron trifluoride etherate being the most effective acid tested at that time [7]. 

The high Lewis acidity, thermal stability and resistance to protic B-C bond cleavage conspire to make B(C6F5)3 an extremely effective activator of organometallic precatalysts for olefin polymerization and other reactions. As a result, other related boranes incorporating perfluoro biphenyl (Chart 1, III,93 IV94), naphthyl (V95) or fluorinated 9-borafluorene (VI96) frameworks have been prepared in an effort to increase the Lewis acidity of the boron center and studied in the context of olefin polymerization. 

The monoaryl boric acids, RB(OH)2, arc usually isolated, as stated al >o x, l)y the action of water on the type RBXg, aitliough in certain cases this leads to the formation of the oxide RBO. The phenyl eom >ound has l)ecn obtained b " boiling with water the product of reaction from magnesium phenyl bromide and boron trifluoride. The most remarkable feature of the type RE(OH)2 is that the action of iiiercuric chloride upon them leads to the production of mercury aryl halides (RHgX). The anisyl and phenetyl compounds do not yield oxides when heated, or form salts, and tlie jS-naphthyl acid exists in two modifications. Dehydration of the acids in maw gives the oxides, RBO. 

Boron a-naphthyl dichloride, CjoHyBClg, boiling at about 164 C. at 25 mm., is prepared by heating mercury di-a-naphthyl and boron trichloride at 120 to 150 for eleven hours. The -naphthyl derivative forms colourless needles, M.pt. 116 C., and is readily soluble in dry benzene, ether, or petroleum ether, fumes slightly in air, and yields the acid with water. 

The catalytic activity of hydrogen chloride was found by Tarbell and Kincaid 34g). Continuing this work, Tarbell et al. 36) showed that certain acids and bases affect the yields of urethanes obtained from a-naphthyl isocyanate and phenols. Thus, catalytic effects were observed with sodium carbonate and acetate, pyridine, triethylamine, acetic acid, trichloroacetic acid, zinc chloride, hydrogen chloride, and boron fluoride etherate. The latter catalyst and triethylamine were found to be the most effective acidic and basic catalysts, respectively. 

Traditionally, aryl bromides/iodides/triflates are employed for coupling with boronates. For example, a-trifluoromethyl vinylboronic acids 129 were utilized for coupling with wide variety of aryl halide substrates such as phenyl, naphthyl, and pyrazyl halides under standard conditions to provide trifluoromethyl-a-arylalkenes 130 (Scheme 28.35). Similarly, 5-vinylboronates 131 were also coupled with aryl halides to provide arylpiperidines 132 (Scheme 28.36). ... 

To rationalize the observed selectivity, the authors propose a two-point binding mechanism first, a Lewis acid-base coordination involving the boron atom, and a van der Waals attraction between the naphthyl group and the enone unit of the a,P-unsaturated carbonyl compound (Figure 5.5) [14]. 

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