Ethylenediamine borane

Devaky and Rajasree have reported the production of a polymer-bound ethylenediamine-borane reagent (63) (Fig. 41) for use as a reducing agent for the reduction of aldehydes.87 The polymeric reagent was derived from a Merrifield resin and a 1,6-hexanediol diacrylate-cross-linked polystyrene resin (HDODA-PS). The borane reagent was incorporated in the polymer support by complexation with sodium borohydride. When this reducing agent was used in the competitive reduction of a 1 1 molar mixture of benzaldehyde and acetophenone, benzaldehyde was found to be selectively reduced to benzyl alcohol. 

Figure 41 The polymer-bound ethylenediamine-borane reagent (63) for use as a reducing agent for the reduction of aldehydes. (Adapted from ref. 87.)...

Various polymer-supported hydrides have been applied successfully to reductions of both carbonyl and olefin groups. Rajasree and Devaky13 describe a cross-linked polystyrene-supported ethylenediamine borane reagent for the selective reduction of aldehydes in the presence of ketones (entry 9). This borane reagent is easily prepared and can be recycled after completion of the reaction. This is a practical alternative to standard borane reagents such as diborane, borane-amine, or borane-sulfide complexes. 

Enantioselective Br2 addition to cyclohexene (11) was accomplished by the solid-state reaction of a 2 1 inclusion complex of 10b and 11 with 7, although the optical yield was low (Sect. 2.1). However, some successful enantioselective solid-state reactions have been reported. For example, reaction of a 1 1 complex of 68 and acetophenone (64a) with borane-ethylenediamine complex (130) in the solid state gave the (i )-(+)-2-hydroxyethylbenzene (65a) of 44% ee in 96%... 

Various procedures for the purification of specific amine-boranes have been reported.12 Ethylenediamine-bisborane can be purified conveniently by aqueous extraction to remove water-soluble impurities. The crude product obtained from the tetrahydrofuran solution is ground to a fine powder in a mortar and added in small portions, with stirring, to about 75 ml. of water which has been cooled in an ice-water bath. Foaming may occur during this treatment. The white crystalline solid which does not dissolve is collected by filtration through a coarse-fritted-glass funnel and washed several times with small portions of cold water (about 5°C.). The final wash filtrate should be neutral toward pH paper. The product is dried by... 

The procedure described for the preparation of ethylenediamine-bisborane is general for the synthesis of amine-boranes and of borane adducts of other electron donors in which elements such as phosphorus and sulfur serve as the donor atom. In addition to the procedure used here for triphenylphosphine-borane, borane adducts of phosphines have been prepared by Analytical reagent grade (Mallinckrodt). 

The tetratoluenesulfonamide may be prepared in five simple steps from ethylenediamine by reaction with thiodiglycollic anhydride in CH2CI2, ethanolysis, ammonolysis, borane reduction and tosylation12. 

The precursor tetratosylamide 22 may be prepared in five steps from ethylenediamine. The reaction sequence (Scheme 3.7) involves diacylation of ethylenediamine with 3-thiadiglycollic anhydride, followed by esterification, ammonolysis, borane reduction and toluenesulfonylation.12 This stepwise synthesis of the desired tetratoluenesulfonamide involving a simple chain elongation strategy is reminiscent of the syntheses of large ring aza-oxa crowns (e.g. [24]-N404) discussed in Chapter 2. 

REDUCTION, REAGENTS Bis(triphenyl-phosphine)copper tetrahydroborate. Borane-Pyridine. Calcium-Methylamine/ ethylenediaminc. Chlorobis(cyclopenta-dienyl)tetrahydroboratozirconium(IV). Chromium(II)-Amine complexes. Copper(0)-lsonitrile complexes. 2,2-Dihydroxy-l, 1-binaphthyl-Lithium aluminum hydride. Di-iododimethylsilane. Diisobutyl-aluminum 2,6-di-/-butylphenoxide. Diisobutyl aluminum hydride. Dimethyl sulfide-Trifluoroacetic anhydride. Disodium tetracarbonylferrate. Lithium-Ammonia. Lithium-Ethylenediamine. Lithium bronze. Lithium aluminum hydride. Lithium triethylborohydride. Potassium-Graphite. 1,3-Propanedithiol. Pyridine-Sulfur trioxide complex. 

Chiral Reagent The diamino phenyl borane (6) derived from (15,25)-l,2-diaminocyclohexane has been used as a chiral proton source for the enantioselective protonation of prochiral cyclic lithium enolates, with ee s up to 93% (eq 9). (15,25)-1,2-Dia-minocyclohexane proved to be highly superior to 1,2-diphenyl ethylenediamine or bis-naphthylamine. 

Solid state reduction of alkyl aryl ketone 8 in an inclusion complex with the chiral host 10 with borane-ethylenediamine complex 2BH3-NH2CH2CH2NH2 gave optically active alcohol 9 in the optical and chemical yields summarized in Table 15-3 [7],... 

This 1 1 complex, a white crystalline solid of considerable stability, is prepared either by heterogeneous absorption of diborane by ethylenediamine in a high vacuum apparatus or by reaction of ethylenediamine with the tetrahydrofurane-borane complex ... 

By a similar method, the (Z)-crotylborate is synthesized from cA-2-butene in 70-75% yield with a 98% isomeric purity. The tartrate esters of allylboronic acids are an excellent reagent for asymmetric allylboration of carbonyl compounds. Allyl(diisopinocampheyl)borane [51] and the allylic boron derivatives of ester and amide, such as camphordiol [52], pinanediol [53], 1,2-diphenyl-1,2-ethylenediamine [54], have also been successfully used for asymmetric allylboration of carbonyls. 

Esters, from diazoketones and organo-boranes, 53, 82 Esters, a-deuterio-, S3, 82 Esters, 7,6-unsaturated by Claisen rearrangement, 53,122 Ethers, by oxymercuration, 53, 96 Ethers, aryl methyl-, selective mono-demethylation of, 53, 93 Ethyl diazoacetate, as source of car-bethoxycarbene, 50, 94 Ethylenediamine, complexes with chromium(II) salts, 52, 62 Ethylene, with p-methoxyphenylacetyl chloride and aluminum chloride to give 6-methoxy-/3-tetralone,... 

The electrolysis of sodium tetrahydroborate in ethylenediamine produces the adduct ethylamine-borane, EtNH2,BH3. This formulation, rather than as the aminoborane EtNHBHg, was suggested by the vibrational spectrum,... 

Borazines of the types 40 [43], 41 [44], 42, and 43 as well as an isomer of 42 (having the sequence NCHiCHgjCHgO instead of N(CH2)30) [43] have been prepared from tris(dialkylamino)-boranes and ethylenediamine or propanediamine derivatives or aminoalkanols in aromatic solvents mass spectral and IR data are given [43, 44]. 41 is used for the preparation of semiconducting, amorphous BNC films (by pyrolysis on various substrates) [44]. 

Besides AB, some of its derivatives have also been investigated for hydrogen storage, especially to overcome the previously mentioned problems. The derivatives hydrazine borane (HB) [13], guanidinium borohydride (GBH) [12], ethylenediamine bisborane (EDB) [43], methylguanidinium borohydride (Me-GBH) [44], and different alkyl amine boranes are the most interesting (Fig. 40.3) [45, 14]. Another compound class between molecular and metal hydride storage materials is that of metal amido boranes, which is not discussed in this chapter [46]. 

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