Boron complexes synthesis

The chiral boron complex prepared in situ from chiral binaphthol and B(OPh)3 is utilized for the asymmetric aza-Diels-Alder reaction of Danishefsky s diene and imines [67] (Eq. 8A.43). Although the asymmetric reaction of prochiral imine affords products with up to 90% ee, the double asymmetric induction with chiral imine by using oc-benzylamine as a chiral auxiliary has achieved almost complete diastereoselectivity for both aliphatic and aromatic aldimines. This method has been successfully applied to the efficient asymmetric synthesis of anabasine and coniine of piperidine alkaloides. 

In spite of its unusual structural outcome, the N-fusion reaction is a very general process. It was observed in a number of other N-confused macrocycles. For instance, an N-fused intermediate forms in the synthesis of trans doubly N-confused porphyrin 96 [238], N-fusion was also induced by the reaction with PhBCl2, in which case the reaction was promoted by the small radius of the coordinating boron(III) center [251], The resulting boron complexes were also aromatic, even though in some cases further chemical modification of the macrocycle took place (as in 110). The fusion process, which appears to be a nucleophilic addition-elimination, is reversible, and N-fused macrocycles can often be reopened when treated with nucleophiles such as alkoxides [248, 249],... 

A similm methodtdqgy was used by Boichardt and coworkers in the synthesis of the phenol (26 Scheme 11). Here, the fact that 4-fluorophenol metallates next to fluorine when the phenol is protected as a TBDMS ether was put to good use for introduction of the hydroxy group, likewise, oxidation of a boron complex was a key step in the synthesis of phenolic dihydrodiols of benzo[a]pyrene, (27) and... 

We have found that chiral boronate complexes with BLA (Brpnsted acid-assisted chiral Lewis acids) to give new catalysts for enantioselective synthesis which achieve selectivity by a double effect of intramolecular hydrogen-bonding interaction and attractive ji-ti donor-acceptor interaction in the transition state by a hydroxy aromatic group [27a],... 

Photochemical methods of synthesis of the phenanthridine system involve the cyclisation of benzanilides and Ifl-benzylideneanilines. The unfavourable geometry of these species and the competing n —> it excitation of the latter, generally result in low yields of the heterocycle. These adverse steric and electronic effects have been largely overcome in the photocyclisation of the boron complexes of A -arylbenzolydroxamic acids, a process which is both fast and high yielding (S. Prabhakar, A.M. Lobo and M.R. Tavares, Chem. Comm., 1978, 884). 

Compared to boron, complexes with aluminum/tm bonds are scarce. Nevertheless, several reaction pathways leading to the synthesis of these compounds exist. 

See also Phosphorus(V) chloride-boron chloride complex, synthesis 24 Phosphorus(V) chloride-gallium(III) chloride complex, synthesis 25... 

Trichloro(tripyridine)chromium(III), synthesis 36 Tris(3-bromoacetylacetonato)chromium(III), synthesis 37 Cyclopentadienyl tricarbonyl hydrides of chromium, molybdenum, and tungsten, synthesis 38 Trichloro(tripyridine)molybdenum(III), synthesis 39 Potassium octacyanotungstate(IV) 2-hydrate, synthesis 40 Chlorine(CP )-labeled thionyl chloride, silicon tetrachloride, boron chloride, germanium (IV) chloride and phosphorus(III) chloride, synthesis 44 Unipositive halogen complexes, synthesis 46 Monopyridineiodine(I) chloride, synthesis 47 Manganese(III) acetylacetonate, synthesis 49 Triiron dodecacarbonyl, synthesis 52... 

Barium iodate 1-hydrate, synthesis 4 Indium(I) bromide, synthesis 6 Hexachlorodisiloxane, synthesis 7 Trichlorosilanethiol, synthesis 8 Tris(acetylacetonato)silicon chloride, synthesis 9 Titanium(III)chloride, synthesis 11 Bis[tris(acetylacetonato)titanium(IV)] hexachloro-titanate(IV), synthesis 12 Zirconium(IV) iodide, synthesis 13 (Triphenyl) aminophosphonium chloride, synthesis 19 (Dimethylamido)phosphoryl dichloride, synthesis 20 Bis(dimethylamido)phosphoryl chloride, synthesis 21 Trimeric and tetrameric phosphonitrilic bromides, synthesis 23 Phosphorus(V) chloride-boron trichloride complex, synthesis 24... 

NMR spectroscopy has been used to determine the thermodynamics of borate ester formation by three readily grafted carbohydrates. Boron specia-tion in borate-poly(amido amine) dendrimer has been performed using B NMR spectroscopy. The role of inositol in the synthesis of FAU- and LTA-type zeolites has been investigated using H, C, Na, and Al NMR spectroscopy. Ulvan-boron complex formation has been studied using B and NMR spectroscopy. The complexation of borate ions and humic acid fractions has been analysed with B and H NMR spectroscopy. ... 

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