Unsymmetrically Substituted Borazines

2-(E)-CH3CH=CH(B3N3H5 (80%) and 2-[CH2=C(CH3)]B3N3Hs (20%) are obtained in an analogous manner to the preceding 2-vinylborazine at 55°C (10 h) in an overall yield of 85%. The isomers have been separated by GLC. Mass spectrum, calculated for Bg Q Ng Hio, nri/z 

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Unsymmetrically -substituted borazines can be prepared by the reaction of IV-substituted borazines or h-trihalogeno-N-substituted borazines and the appropriate amount of Grignard reagent (94). Borazines unsymmetrically substituted on nitrogen have been prepared by the reaction of Hthium borohydride and ammonium chloride and alkyl ammonium chlorides (105,106), and by Uthiation of B- trime thylb o r azine followed by reaction with alkyl halides (107). 

Direct synthesis of unsymmetrical substituted borazines has been reported infrequently. The feature of borazines with unsymmetrical substitution at the boron atoms resides in the fact that 2-organo- or 2,4-diorgano-borazines may be utilized in polycondensation reactions to yield insoluble compounds of macroscopic linear structure. 

In principle, the synthesis of unsymmetrically substituted moieties of borazine may be achieved by the same reactions which are suitable for preparing the symmetrical compounds. 

Unsymmetrically substituted tetra- and penta-n-butyl borazines are obtained by thermal decomposition of dibutylazidoborane 100> with the elimination of butene. Because of the hazards of handling boron azides, this method cannot be recommended. 

Unsymmetrically substituted aminoborazines resulted from the reaction of amines with B-alkylthioborazines 144>. The first optically active borazine has been obtained from the reaction of 2,4,6-trichloroborazine and (+)2-butylamine 145> using triethylamine as a hydrogen chloride acceptor. B-Monoaminoborazine, HaNsBaH NH ) and isotopically labeled derivatives thereof have been prepared by photochemical reaction from borazine and ammonia in a gas phasereaction 14fi-147>. 

The unsymmetrical B -substituted borazine derivatives H(X)(Y)B3N3H3, where X = C1, Y=OCN X = C1, Y = CN X = CN, Y = OCN X=OCN, Y = OCN X = CN, Y = CN, have been prepared by the reaction of the appropriate B-substituted chloroborazine with an Ag1 salt.295 It was found that H atoms in B -substituted borazines, unlike those in H3B3N3H3, are inert to attack by an Ag1 salt, giving the first evidence for a substituent effect in borazine chemistry. 

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