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Amino diboranes

Aminoboration, of irainoboranes, 31 155 Aminoborazines, 16 241 Aminochlorocyclophosphazene, 21 56 Amino diboranes, 2 289, 216-219, 247 Aminodichlorophosphorane, dehydrohalogena-tion, 21 46... [Pg.10]

Several transamination reactions of B2(NMe2)4 20 with secondary amines have led to mixed tetra(amino)diborane(4) compounds B2(NMe2)4 ra(NR2)ra 24-26 (Scheme 5), and B2(NC5H10)4 23 has been characterized by an X-ray structure analysis which reveals the presence of a rather long B-B bond (Fig. 3). [Pg.196]

However, tetra(amino)diboranes(4) of type R2N(Me2N)B-B(NMe2)NR2 are more readily accessible from LiNR2 and B2(NMe2)2Cl2. Similarly,... [Pg.196]

A series of mixed tetra(amino)diborane(4) compounds bearing pyrrolyl, indolyl, and carbazolyl substituents besides dimethylamino groups has been prepared and subjected to reduction with elemental lithium in the... [Pg.202]

Table 3 Structural parameters for p-amino-diborane, H2N—B2H5... Table 3 Structural parameters for p-amino-diborane, H2N—B2H5...
MO calculations on bis(amino)diborane(4) H2l4— BH—BH— NH2 and (amino)vinylborane H2C=CH—BH— NH2 have been used to rationalize differences in the photochemical reactivity of C==C—C=C and... [Pg.140]

Reaction of diborane and tetraarylstannanes brings about transmetallation in which one or more aryl group is transferred to boron.The course of the reaction between dimethylbis(phenyl-ethynyl)stannane and trialkyIboranes can be followed by Sn n.m.r. spectroscopy which is also useful in observing the distribution of products in the final mixture. 1,2-Di-tert--buty1-1,2-dichlorodiborane (4) and 1,2-dichloro-l,2-bis(dimethyl-amino) diborane (4) add to 1-triraethylsilylalkynes to give... [Pg.31]

Reduction to Amino Alcohols. Reduction can be brought about using diborane—dimethyl sulfide in THF (80). NaBH in ethanol is also... [Pg.280]

The most successful of the Lewis acid catalysts are oxazaborolidines prepared from chiral amino alcohols and boranes. These compounds lead to enantioselective reduction of acetophenone by an external reductant, usually diborane. The chiral environment established in the complex leads to facial selectivity. The most widely known example of these reagents is derived from the amino acid proline. Several other examples of this type of reagent have been developed, and these will be discussed more completely in Section 5.2 of part B. [Pg.110]

Bell and Hall have incorporated an organometallic unit into a crown by using the ferrocenyl unit as part of the ring or as a third strand. The unit is incorporated either as the 1,1 -diformylferrocene or the corresponding acid. In the former case, the bis-imine is prepared and reduced to give the saturated crown (see structure 24). In the latter case, the acid is converted into its corresponding chloride and thence into the diamide by reaction with a diamine. Diborane reduction affords the saturated amino-crown. Structure 24 could be prepared by either of these methods but the dialdehyde approach was reported to be poor compared to the amide approach which afforded the product in ca. 60% yield . [Pg.53]

Benzoxazole reagieren mit Diboran in 1,2-Dimethoxy-athan bei 25° unter Amin-Boran-Bildung, nachfolgender Umlagerung und Verseifung der 2,3-Dihydro-(benzo-1,3,2-oxazaborole), mit Salzsaure zu den entsprechenden o-Amino-phenolen2 ... [Pg.91]

Diboran kann besonders dann zur Reduktion von Nitrilen mit Erfolg eingesetzt werden, wenn Lithiumalanat und auch Lithiumalanat/Aluminiumchlorid nicht die gewunschten Resultate zeigen. Aus tert.-Butyl-malonsaure-dinitril erhalt man z.B. nur durch Reduktion mit Diboran l-Amino-3,3-dimethyl-2-aminomethyl-butan (36—48% d. Th.)2. [Pg.114]

Mit aquivalenten Mengen Diboran wird dagegen die Cyan-Gruppe selektiv hydriert, so erhalt man z.B. aus Phenyl-glyoxylsaure-nitril 61% d.Th. to-Amino-acetophenon (s.S.159) ... [Pg.118]

Aus Amino-alkansauren mit N-Alkyl- oder N-Aryl-Substituenten werden leichter losli-che Komplexe erhalten2. 4-Alkylamino-butansauren3 werden durch Lithiumalanat relativ leicht zu den entsprechenden Pyrrolidinen cyclisiert. Zur selektiven Reduktion der Carboxy-Gruppe von N-acylierten Aminosauren ist Diboran geeignet4 5 z.B.6 ... [Pg.163]

Lithiumalanat reduziert l-Alkyl-indolyl-(3)-glyoxylsaure-amide nur zu den 3-(2-Amino-1-hydroxy-athyl)-1- alkyl-in dolen (vgl. a. S. 241), wahrend mit Diboran die vollige Reduktion der Seitenkette moglich ist. Allerdings werden meist Gemische gebildet z. B.5 ... [Pg.242]

To prepare the diborane in tetrahydrofuran, add 0.3 M NaBH4 (or LiBH4) and 0.4 M BF3 in total 200 ml tetrahydrofuran and keep dry in refrigerator, or generate the diborane in the reaction flask as follows To a well-stirred suspension of 3.4 g NaBH4 in 150 ml tetrahydrofuran and 0.3M of the styrene or propenylbenzene, add over one hour at room temperature, 15.1 ml BF3 in ether in 20 ml tetrahydrofuran (keep temperature at room temperature) let stand one hour at room temperature and decompose the excess hydride with water then add the NaOH and chloramine (or hydroxyl-amino-O-sulfonic acid) and proceed as above to get the amine. [Pg.95]

Enantioselective reduction of ketones.1 The ability of diborane in combination with the vic-amino alcohol (S)-2-amino-3-methyl-l,l-diphenyl-l-butanol (12, 31) to effect enantioselective reduction of alkyl aryl ketones involves formation of an intermediate chiral oxazaborolidine, which can be isolated and used as a catalyst for enantioselective borane reductions (equation I). [Pg.239]

Alkali metal borohydrides are frequently used for the reduction of rc-electron-deficient heteroaromatic systems, but reduction of jt-electron-excessive arenes is generally possible only after protonation of the systems [e.g. 35-37]. The use of tetra-n-butylammonium borohydride under neutral conditions for the conversion of alkylindoles into indolines [38] is therefore somewhat unusual. Reduction of indoles by diborane under strongly alkaline conditions involves the initial interaction of the indolyl anion with the diborane to form an amino-borane which, under the basic conditions, reacts with a second molecule of diborane to produce the indoline [39]. The reaction of tetra-n-butylammonium borohydride with indoles could also proceed via the intermediate formation of diborane. [Pg.487]

The asymmetric reduction of oximes of 2-trifluoroacetyl furan, by using diborane with a chiral amino alcohol, has also allowed synthesis of both enantiomers of trifluoroalanines in an elegant manner. The key step in this synthesis is the separation of the (Z) and ( ) isomers of the oximes (Figure 5.4). ... [Pg.150]

In gleicher cheraischer Ausbeute, jedoch mit einer optischen Ausbeute von 76%, laBt sich Acetophenon-(O-methyl-oxim) mit Lithium-alanat in Gegenwart eines aus Diboran und (S)-2-Amino-3-methyl-l,l-diphenyl-butanol gebildeten Boran-Adduktes zu (S)-l-Amino-1-phenyl-ethan reduzieren2. [Pg.881]


See other pages where Amino diboranes is mentioned: [Pg.379]    [Pg.200]    [Pg.205]    [Pg.229]    [Pg.232]    [Pg.379]    [Pg.200]    [Pg.205]    [Pg.229]    [Pg.232]    [Pg.28]    [Pg.164]    [Pg.76]    [Pg.170]    [Pg.121]    [Pg.77]    [Pg.86]    [Pg.118]    [Pg.154]    [Pg.161]    [Pg.163]    [Pg.164]    [Pg.238]    [Pg.381]    [Pg.981]    [Pg.49]    [Pg.1125]    [Pg.1518]    [Pg.881]    [Pg.881]   
See also in sourсe #XX -- [ Pg.289 ]




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