Bifunktionelle und cyclische Organomagnesiumverbindungen, II¹⁾ 1‐Oxa‐5‐magnesiacyclooctan

Abstract

Durch Assoziationsmessungen wird festgestellt, daB die aus 3.3'-Dibrom-di-n-propylather (3) erhaltliche Di-Grignard-Verbindung 1 in Tetrahydrofuran vollstandig zu monomerem I-Oxa-5-magnesiacyclooctan (2) und Magnesiumbromid disproportioniert. Die Bevorzugung von 2 wird auf intramolekulare Koordination zwischen Magnesium und Sauerstoff zuriickgefuhrt. Bei hoherer Temperatur zersetzt sich 2 zu Cyclopropan und trimerem 1 -0xa-2-magnesiacyclopentan (6a). Bifunctional and Cyclic Organomagnesium Compounds, II. -I-Oxa-5-magnesiacyclooctaneFrom association measurements it is concluded that the di-Grignard compound 1 formed from 3,3'-dibromodi-n-propyl ether (3) in tetrahydrofuran completely disproportionates to monomeric I-oxa-5-magnesiacyclooctane (2) and magnesium bromide. The preference for 2 is ascribed to intramolecular coordination between magnesium and oxygen. At higher temperatures 2 decomposes to cyclopropane and trimeric I-oxa-2-magnesiacyclopentane (6a).

Dilithium and Magnesium Alkanediides and 1‐Oxaalkanediides

“…Insertion of an oxygen atom between the two middle carbon atoms led to [BrMg(CH 2 ) 3 ] 2 O, which immediately eliminated MgBr 2 yielding 1-oxa-5-magnesiacyclooctane. [41] After these initial preparations of bis-Grignard reagents [(BrMg) 2 -n] as well as magnesiacycloalkanes (Mg-n), the chemical properties and applications for diverse derivatization reactions were investigated and summarized in several early review articles. [31,[42][43][44][45] Reduction of Br(CH 2 ) n Br with n Յ 3 led to side reactions and it was impossible to isolate pure bis-Grignard reagents; reduction of 1,3-dibromopropane (n = 3) with magnesium gave BrMg(CH 2 ) 3 MgBr [(BrMg) 2 -3] with a yield of approx.…”

“…Insertion of an oxygen atom between the two middle carbon atoms led to [BrMg(CH 2 ) 3 ] 2 O, which immediately eliminated MgBr 2 yielding 1‐oxa‐5‐magnesiacyclooctane . After these initial preparations of bis‐Grignard reagents [ (BrMg) 2 ‐n ] as well as magnesiacycloalkanes ( Mg‐n ), the chemical properties and applications for diverse derivatization reactions were investigated and summarized in several early review articles , .…”