Boronic ester bridges

For examples see a) Wiederrecht, G.P., M.R Niemczyk, W.A. Svec, and M.R. Wasielewski (1996). Ultrafast photoinduced electron transfer in a chlorophyll-based triad VibrationaUy hot ion pair intermediates and dynamic solvent effects. J. Am. Chem. Soc. 118(1), 81-88 and b) Shiratori, H., T. Ohno, K. Nozaki, I. Yamazaki, Y. Nishimura, and A. Osuka (1998). Coordination control of intramolecular electron transfer in boronate ester-bridged donor-acceptor molecules. Chem. Commun. (15), 1539-1540. 

Arimori et al utilized the electrostatic interaction to generate dimeric boronic acid-appended porphyrins. Anionic porphyrin 25 and cationic porphyrins 16 form 1 1 complexes, which give the specific exci ton-coupling bands in CD spectroscopy only in the presence of glucose and xylose. The CD sign is characteristic for the absolute configuration of the saccharides. Structural examination established that only these monosaccharides can bridge two porphyrins by ester formation with boronic acid and twist them asymmetrically. 

Boron-oxygen-boron bridged gluconatoborate (76) and related conq>lexes of boron with gluconate ions have been prepared and characterized by a variety of analytical techniques. The examination by "B- and C-n.mx. spectroscopy of borate esters derived firom carbohydrate oximes in solution indicated the formation of relatively stable 6-membered borate ester rings between the oxime-OH and C-2-0H. ... 

Reactions of Alhyl and Aryldiboranes a. Hydrolysis, Alcoholysis, and Elated Reactions. As with diborane, the bridge and terminal boron-bonded hydrogens of alkylated diboranes are normally quite labile at room temperature toward hydrolysis and alcoholysis 28, 52, 53, 58-62, 78, 79). Since the alkyl-boron bonds are not usually cleaved, the alkylboronic or alkylborinic acids (or esters in the case of alcoholysis) produced are often quite useful in determining the structure of the original alkylated diborane. Similarly, dialkylthioborinic esters are... 

Liu T, Chen Y, Zhang K et al (2001) Enantiomeric recognition of chiral 3,3-bridged-l,r-binaphthol dimer toward a-phenylethylamine and a-amino acid ester. Chirality 13 595-600 Beer G, Daub J, Rurack K (2001) Chiral discrimination with a fluorescent boron-dipyrromethene dye. Chem Commun 1138-1139... 

Figure 23 Morrison s proposed complexes of the cis-1,2-cyclopentanediol ester of 8-quinolineboronic acid with solvent water and phenol molecules bridging the nitrogen and boron centres. Blue bonds are used to represent dative bonding.

Incorporation of this coordinative amine ligand within the cycle structure is an alternative approach for generating stable macrocycles. In this regard, alkyl bridged bis(2-hydroxyphenylmethyl) amines have been reacted with 4,4 -biphenyldiboronic acid (Fig. 19a). Esterification proceeds with concomitant coordination of the amine to the resulting ester. The paraquat dication is complexed by this assembly in a 1 1 manner (Fig. 19b) through ionic interactions (anionic boronate with pyridyl cation), attractive n-n interactions (between biphenyl components) and C —H —O hydrogen bonds (paraquat... 

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