Potassium tris borate, reaction with

Reaction of [RuC12(C6H6)]2 (la), in acetonitrile, with pyrazole, 3,5-dimethylpyrazole, or potassium tris(3,5-dimethylpyrazolyl)borate, K[HB-(Me2pz)3], proceeds by substitution of all chlorides and affords complex 16 (Scheme 1), resulting from the coupling of acetonitrile with pyrazole (22). The reaction of la with tetrakis(l-pyrazolyl)borate ion in boiling acetonitrile, however, led to the trisubstituted derivative 17, the structure of which was established by an X-ray diffraction study (26). 

Lithiumlithium triethylaluminum, sodium triethylboron, sodium triethanolamine borate,- potassium triethylboron and tri-n-butyltin cyclohexanone enolates have been successfully monoalkyl-ated. In Scheme 6 the behavior of the lithium enolate of cyclohexanone (11) and the lithium triethylaluminum enolate upon reaction with methyl iodide is compared. The latter enolate gives better results since no dimethylation products were detected, but clearly the cyclohexanone enolate (11) is much less prone to dialkylation than the cyclopentanone enolate (10). Scheme 6 also provides a comparison of the results of alkylation of the potassium enolate of cyclohexanone, where almost equal amounts of mono- and di-alkylation occurred, with the alkylation of the potassium tiiethylboron enolate where no polyalkylation occurred. The employment of more covalently bonded enolates offers an advantage in cyclohexanone monoalkylations but not nearly as much as in the cyclopentanone case. 

Darses and co-workers have published a series of papers on the synthesis of stereo-defined trisubstituted alkenes by the coupling of readily available unreactive MBH adducts with either organoboronic acids or potassium tri-fluoro(organo)borates in the presence of a rhodium complex via a reaction pathway involving a 1,4-addition/p-hydroxy elimination mechanism. Compared with the aforementioned Pd-catalyzed cross-coupling reaction, this reaction does not need the activation of the hydroxyl group with acetate or carbonate therefore it is more desirable, particularly in terms of atom economy. For the MBH adducts derived from methyl acrylates, the initial reported catalyst, [ Rh-(cod)Cl 2], was active at 50 °C for boronic acids and at 70 °C... 

Reaction of potassium tris(pyrazolyl)borate with [Pd(Me)2(pyridazine)] or [Pd(Me)(Ph)(tmeda)] produces the anions [Pd(Me)(R)(HB pyrazolyl 3)], R = Me, Ph respectively. Treatment with wet ketone produces the Pd(IV) alkyls [Pd(Me)2(R)(HB pyrazolyl)3)]. The trimethyl product has been ciystallographically charactmsed. The net reaction is oxidation of Pd(II) by water accompanied by a methyl group transfer. Allenyl and propargyl halides add trans across the metal centres in [Pd(PPh3)4] and [Pt(PPh3)4], The isomerisation of the o- allenyl products [M(X)(CH=C=CRR )] has been studied and the crystal structure of one example has been determined. 

Several research groups have studied the chemistry of tris(pyrazolyl)borate tricarbonyl complexes of technetium and rhenium. As depicted in Scheme 28, these studies allowed the synthesis of/ac-[M(CO)3Tp ] [M is Tc, Re, Tp is Tp (111/113), Tp (112/114)] complexes, which were all structurally characterized. Complexes 111-114 were synthesized by reaction of the classical starting materials [M(CO)5Br] with the sodium or potassium salts of the correspondent Tp ligands [121-123]. 

Regioselective alkylations at C-6 of 2-methylcyclohexanone have been accomplished via the alkylation of thermodynamically unstable trisubstituted lithium, lithium triethanolamine borate, potassium triethylboron, tri- -butyltin and benzyltrimethylammonium enolates (c/. 2). Alkylation is faster than equilibration for the more reactive alkylating agents. Although enolate equilibration has been shown to compete with butylation using n-butyl iodide under certain conditions, butylation of the enolate (2 M = Li) in liquid ammonia-THF gave a mixture of cis- and /ra/ij-2-methyl-6-butylcyclohexanone along with 2-methylcyclohexanone in an 83 17 ratio in 90% yield no 2,2-dialkylcyclohexanone was obtained in this reaction (Scheme 8). ... 

Although the ratio of biaryls formed in these halogenative oxidations is somewhat sensitive to the reaction medium, it is noteworthy that the amount of biaryl formation is quite dependent both on the nature of the solvent and the metal ion (L, Na" ", or K+). Although potassium phenyl(tri-/7-tolyl)borate (58) dissolved in chloroform reacted with iodine to yield a 1.4 1.0 ratio of biaryl to p-iodotoluene, the same reaction in dimethylformamide gave almost exclusively p-iodotoluene. Likewise, the sodium analog of 58 gave a biaryl p-iodotoluene ratio of 1 32 (48). 

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