ISSN:
0009-2940
Keywords:
Alkylidenoboranes
;
1,2-Oxaboretanes
;
1,2,4-Azasilaboretidines
;
2,3-Diiminoboretane
;
Borylsilyldiazomethane
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Reactions at the BC Double Bond of iPr2N=B=C(SiMe3)2By thermal elimination of propene and migration of a methyl group at 500-600°C, the alkylidenoaminoborane iPr2N=B=C(SiMe3)2 (1b) is transformed to the azasilaboretidine [-N(iPr)=B(Me)-CH(SiMe3)-SiMe2-] (2). Protic agents HX (X = Cl, Br, OMe, OiPr, NMe2, NEt2) are added to 1b to give iPr2N=B(X)-CH(SiMe3)2 (3a-f); products 3g, h of the same type (X = O—CR=CH2, R = tBu, Ph) are formed from 1b and ketones MeRCO. Products iPr2N=B(X)-C(SiMe3)2-Y [X = Y = Br: 4; X = Me, Y = Li(tmeda): 5] are isolated from the reaction of 1b with the unpolar Br2 or with LiMe, respectively; adduct 5 can be hydrolyzed to 3i (X = Me, Y = H) by HCl. The bromoboration of 1b by MeBBr2 or BBr3 gives iPr2N=B(Br)-(Z)C(SiMe3)-BBrMe (Z = SiMe3: 6a; Z = SiMe2Br: 6b). The CO group of aldehydes RCHO [R = Me, tBu, C(Me)=CH2], ketones PhRCO (R = Me, Ph), and ethyl acetate undergo a [2+2] cycloaddition with 1b to give oxaboretanes [-B(NiPr2)-C(SiMe3)2-CRR′-O-] (7a-f); starting with HCONMe2, the cycloaddition to 1b is followed by ring opening and the migration of a silyl group to yield (iPr2N)B(OSiMe3)-C(SiMe3)=CH(NMe2) (8). Azides RN3 (R = Ph, PhCH2) may be added to 1b with loss of N2, azaboriridines [-(iPr2N)B—C(SiMe3)2-NR-] (9a, b) being formed, whereas Me3SiN3 gives the diazo compound (iPr2N)B[N(SiMe3)2]-C(SiMe3)=N2 (10). The formation of the boretane [-(iPr2N)B—C(SiMe3)2-C(=NtBu)-C(=NtBu)-] (11) is observed from the 2:1 reaction of tBuN≡C with 1b. The alkylidenoaminoborane H14C7N=B=C(SiMe3)2 (1c; H14C7N = 2,6-dimethylpiperidino) is synthesized by a procedure similar to the synthesis of 1b and gives reactions similar to those of 1b: thermal cyclisation to the azasilaboretidine 12, addition of HNMe2 to give 3j, [2 + 2] cycloaddition of RCHO (R = tBu, Ph) and Ph2CO to give 7g-i.
Notes:
Das Alkylidenaminoboran iPr2N=B=C(SiMe3)2 (1b) geht bei 500-600°C unter Propenabspaltung und Methylwanderung in das Azasilaboretidin [-N(iPr)=B(Me)-CH(SiMe3)-SiMe2-] (2) über. Protische Stoffe HX (X = Cl, Br, OMe, OiPr, NMe2, NEt2) addieren sich an 1b zu iPr2N=B(X)—CH(SiMe3)2 (3a-f); die Produkte 3g, h desselben Typs (X = O—CR=CH2; R = tBu, Ph) erhält man mit Ketonen MeRCO. Weiterhin kann man an 1b das unpolare Br2 sowie LiMe unter Bildung von iPr2N=B(X)—C(SiMe3)2-Y addieren [X = Y = Br: 4; X = Me, Y = Li(tmeda): 5]; 5 wird durch HCl zu 3i verseift (X = Me, Y = H). Die Bromoborierung von 1b mit MeBBr2 und BBr3 führt zu iPr2N=B(Br)—(Z)C(SiMe3)-BBrMe (Z = SiMe3: 6a; Z = SiMe2Br: 6b). Die CO-Gruppe von Aldehyden RCHO [R = Me, tBu, C(Me)=CH2], Ketonen PhRCO (R = Me, Ph) und Ethylacetat geht mit der BC-Bindung von 1b [2 + 2]-Cycloadditionen zu den Oxaboretanen [-B(NiPr2)-C(SiMe3)2-CRR′-O-] (7a-f) ein; im Falle von HCONMe2 folgt der Cycloaddition eine Silylverschiebung unter Ringöffnung zu (iPr2N)B(OSiMe3)-C(SiMe3)=CH(NMe2) (8). Azide RN3 (R = Ph, PhCH2) addieren sich an 1b unter Abspaltung von N2 zu den Azaboriridinen [-(iPr2N)B—C(SiMe3)2-NR-] (9a, b), während das Azid Me3SiN3 unter Silylwanderung die Diazoverbindung (iPr2N)B[N(SiMe3)2]-C(SiMe3)=N2 (10) ergibt. Mit tBuN≡C reagiert 1b im Verhältnis 2:1 zum Boretan [-(iPr2N)B—C(SiMe3)2-C(=NtBu)-C(=NtBu)-] (11). Das Alkylidenaminoboran H14C7Nd—B=C(SiMe3)2 (1c, H14C7N = 2,6-Dimethylpiperidino) bildet sich ähnlich und reagiert analog 1b: thermische Cyclisierung zum Azasilaboretidin 12, Addition von HNMe2 zu 3j, [2+2]-Cycloaddition von RCHO (R = tBu, Ph) und Ph2CO zu 7g-i.
Additional Material:
2 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19891220402
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