Ein einfacher Weg zu Organogalliumverbindungen

Abstract

Versuch, aus (22R.25 S)-N-Chlor-22.26-imino-5cr-cholestan-3p-01 ( I ) [2] durch Erhitzen (75 min) rnit 5-proz. methanolischer Kalilauge unter HC1-Abspaltung das cyclische Azomethin (3) darzustellen, erhielten wir in 57-proz. Ausbeute das Solanurn-Steroidalkaloid Demissidin (2), Fp = 218 b.s 22OoC, [a]g = +26,9 ". Durch sorgfaltige Chromatographie des Reaktionsproduktes an AI2O3 lieBen sich neben ( 2 ) und 24 % entchloriertem Ausgangsmaterial 3,5 % der gewunschten A2z(N)-ungesattigten Verbindung ( 3 ) , F p = 190 bis 193 "C, [ L Y ]~ = -40,6 ' , IR-Bande bei 1661 cm-1, gewinnen. lm Gegensatz dazu liefert das (22S.25R)-Stereoisomere von ( I ) unter den gleichen Bedingungen 60 % des erwarteten (25R)-Azomethins, jedoch kein Solanidan [3]. Fur die Bildung von (2) aus ( I ) mu8 eine direkte HCI-Abspaltung unter Beteiligung der nicht aktivierten CH-Bindung an C-16 angenommen werden. Die Ursache fur diesen anomalen Octahydropyrrocolin-RingschluR diirfte in einer besonders giinstigen sterischen Anordnung der an der Reaktion beteiligten Zentren und in der Stabilitat des gebildeten (22 R.Z5S)-Solanidan-Geriistes zu suchen sein. Eingebanpen am 9. Marz 1964 [Z 6921 Auf Wunsch der Autoren erst jetzt veroffentlicht [I 1 Solununz-Alkaloide, 42. Mitteilung. -41. Mitteilung. K. Sshreiter u. G. Adam, Chem. Ber., im Dmck. [2] G.

Group 13 decamethylmetallocenium cations

“…Low-resolution mass spectra (CI, CH 4 ) were obtained on a Finnigan MAT TSQ 700 instrument. High-resolution mass spectra (CI, CH 4 ) were obtained on a VG ZAB-VE sector instrument.The starting materials MeGaCl 2 ,42 Cp*M (M = Li, Na, K),1 Cp* 2 BCl,5 Cp* 2 BMe,15 Cp* 2 AlMe, 10 "Cp* 2 AlCl",11 Cp* 2 GaCl,22 Cp* 3 Ga,29 [Li][B(C 6 F 5 ) 4 ],43 [Ph 3 C][B(C 6 F 5 ) 4 ],44 Al(C 6 F 5 ) 345 and Ga(C 6 F 5 ) 345 were prepared according to published procedures.The preparations of the salts [Cp* 2 B][AlCl 4 ], 6 [Cp* 2 Al][AlCl 4 ], 12 and [Cp* 2 Ga][BF 4 ] 14 have been reported previously.…”

Transmetalation as a Route to a Cyclic Heteronuclear Bifunctional Lewis Acid Containing Tin and Gallium

“…In this paper, we report that tin−gallium ligand exchange occurs between 1,8-bis(trimethylstannyl)naphthalene ( 1 ) and gallium trichloride to yield a heteronuclear bifunctional Lewis acid with a central eight-membered stannagallacycle. Organotin reagents are often employed for the arylation, vinylation, and alkylation of boron halides. ,− Such reactions are not limited to boron and have been observed on a few occasions with aluminum halides. ,, To our knowledge, however, this synthetic strategy has not been previously applied to the preparation of organogallium species. , …”

Bis(dimethylamido) Complexes of Alkyl- and Phenylgallium. Useful Precursors to the RGa2+ Synthon

“…A method was needed to differentiate the reactivity of the alkyl from the two other ligands. The known alkyl and aryl dihalides, [RGaX 2 ] 2 , − suffer from the acidity of [NH 4 ]X, which would form as a byproduct in ammonia and which could lead to protonolysis of the desired alkyl ligand. In addition, should the desired oligo- or polymeric organogallium imide be insoluble, separation from [NH 4 ]X might prove difficult.…”