Reactions phenylboration

DCE interface in the presence of TPBCl [43,82]. The accumulation of products of the redox reactions were followed by spectrophotometry in situ, and quantitative relationships were obtained between the accumulation of products and the charge transfer across the interface. These results confirmed the higher stability of this anion in comparison to TPB . It was also reported that the redox potential of TPBCP is 0.51V more positive than (see Fig. 3). However, the redox stability of the chlorinated derivative of tetra-phenylborate is not sufficient in the presence of highly reactive species such as photoex-cited water-soluble porphyrins. Fermin et al. have shown that TPBCP can be oxidized by adsorbed zinc tetrakis-(carboxyphenyl)porphyrin at the water-DCE interface under illumination [50]. Under these conditions, the fully fluorinated derivative TPFB has proved to be extremely stable and consequently ideal for photoinduced ET studies [49,83]. Another anion which exhibits high redox stability is PFg- however, its solubility in the water phase restricts the positive end of the ideally polarizable window to < —0.2V [85]. 

Parshall (65IC52) carried out this reaction with bis(hydroxyalkyl)phos-phine obtained from phosphine and hexafluorocyclobutanone and diethyl ester of phenylboric acid [Eq. (53)]. 

But in the presence of pyridine, l-borata-2,6,7-trioxa-4-phosphabi-cyclo[2,2,2]octane (109) has been obtained [Eq. (65)]. The course of the reaction does not depend on the replacement of phenylboric acid anhydride by its ester (85IZV469 86JZVI641). 

The possibility of carrying out a multistep synthesis makes it possible to obtain P,B-containing derivatives from unstable intermediate a-hydroxyalkylphosphines. Thus, phenylphosphine, salicylic aldehyde, phenylboric acid anhydride, and triethylamine interact to give a bicyc-lic product—2,8,9-trioxa-1 -borata-4-phospha-6,7 -benzobicyclo [3,3,3] nonane (115) [Eq. (74)] (87IZV2118 89IZV946). In this case an aldehyde takes part in the reaction opening up new synthetic possibilities. 

Recently, addition of organorhodium species to nitriles has been reported.420 4203 4201 Intermolecular reaction of benzonitrile with phenylborate (accompanied with r//w-aryiation) (Equation (65)), arylative cyclization of acetylenic nitriles (Equation (66)), and cyclization of 2-cyanophenylboronic acid with alkynes or strained alkenes (Equation (67)) are proposed to proceed via this process. 

Phenanthrenequinone from benzoin. The photocyclization of stilbene to phenanthrene requires a trans to cis isomerization. This step can be circumvented by reaction of benzoin with phenylboric acid to form the 1,3-dioxoborole 2. This adduct can be converted to phenanthrenequinone by photocyclization in the presence of diphenyl diselenide as the oxidant. 

Since few salts are sparingly soluble in water, there are few precipitation reactions of the aqueous ions. Generally the larger the M+ ion, the more numerous are its insoluble salts. Thus sodium has very few the mixed Na—Zn and Na—Mg uranyl acetates [e.g., NaZn(U02)3(CH3C02),-6H20], may be precipitated almost quantitatively under carefully controlled conditions from dilute acetic acid solutions. The perchlorates and hexachloroplatinates of K, Rb, and Cs are rather insoluble in water and virtually insoluble in 90% ethanol. These heavier ions may also be predpitated by the ion [Co(N02)6]3 and various other large anions. Sodium tetra-phenylborate Nal QHs), which is moderately soluble in water, predpitates the tetraphenylborates of K, Rb, and Cs from neutral or faintly acid aqueous solutions. 

Poly(iminoborane)s [(-BR=N-)n] are a potential 7t-conjugated polymers, since boron-nitrogen bonds possess the double bond like nature owing to pTt-pjt interaction However, these materials are not fully characterized so far 10>. In order to incorporate the monomeric B-N bond into the conjugation path, we examined an alternating boration copolymerization between diisocyanates and diynes making use of different reactivity between haloboration and phenylboration reactions. 

As depicted in Scheme 4, the treatment of 1,4-diethynylbenzene with 2eq. of diphenylbromoborane (selective haloboration) and the subsequent reaction with leq. of tolylene-2,4-diisocyanate (phenylboration polymerization) gives the corresponding alternating copolymers. 

Vanadium hexacarbonyl reacts with various arenes yielding complexes [(arene)V(CO)4]" [V(CO)6] from which hexafluorphosphate or tetra-phenylborate salts can be prepared by metathesis reaction (50, 52). The cation [(CeHe)V(CO)4] reacts with NaBH4 to give the neutral cyclo-hexadienyl compound (CeH7)V(CO)4 (51). Similar results are observed with methyl-substituted derivatives. The addition of the hydride ion was shown to occur preferentially at unsubstituted positions of the aromatic ring. 

A third synthetic route that has been successfully exploited in the formation of five- and six-membered heterocycles has been studied in an attempted synthesis of a borirene derivative. Reaction of phenylboron dibromide with tolan gives a mixture of products resulting from both haloboration and phenylboration 109). A Wurtz coupling reaction of the former derivative could generate a borirene derivative... 

Strong evidence for this model is provided by an elegant substrate-catalyzed single-turnover experiment presented by Sadow and coworkers [81]. The four-coordinate Cs-symmetric magnesium tris(oxazoline)borate alkyl complex [To MgMe] (To = tris(4,4-dimethyl-2-oxazolinyl)phenylborate) excludes additional ligands from the coordination sphere and is a competent precatalyst for the hydroamination of l-aminopent-4-enes. In line with the expectations furnished by the aforementioned systems, the reaction of l-amino-2,2-diphenylpent-4-ene follows the empirical rate law v = / obs[aminoalkene] [catalyst], with a KIE of... 

The reactions of phenylboric acid with substituted silazanes and siloxanes have produced ring systems of the type (33) and (34) for the first time. ... 

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