Über enolisierte Derivate der Chlorophyllreihe. 132‐Desmethoxycarbonyl‐173‐desoxy‐132,173‐cyclochlorophyllid a‐enol und eine Methode zur Einführung von Magnesium in porphinoide Ligandsysteme unter milden Bedingungen. (Vorläufige Mitteilung)

Enol derivatives in the chlorophyll series. 132‐Desmethoxycarbonyl‐173‐desoxy‐132,173‐cyclochlorophyllide a‐enol and a method for the introduction of magnesium into porphinoid ligands under mild conditions Magnesium transfer from the iodo‐magnesium salt of 3,5‐di‐t‐butyl‐4‐hydroxy‐toluene (BHT) into methyl pheophorbide a is a fast process in methylenechloride/ether solution at ambient temperature. This procedure for the introduction of magnesium into labile chlorin ligands has made possible the preparation of a crystalline 132, 173‐cyclochlorophyllide a‐enol. Concomitant use of the lithium salt of BHT facilitates the more critical insertion of magnesium into methyl bacteriopheophorbide a. The preparative success of these magnesium transfers depends crucially upon the solvent system used. Under conditions where the complexation of methyl pheophorbide a with iodo‐magnesium‐BHT is essentially complete within 2 minutes at 12° in methylenechloride/ether solution, strong inhibition of the magnesium transfer is observed by cosolvents such as pyridine, dimethylacetamide, dioxan or tetrahydrofuran.