Cymantrene-based iminodiamidophosphites: the first phosphite-type ligands with planar chirality

Synthesis of a 2-benzocymantrenylpyridine and further mechanistic insights

“…Ligand 1 was subsequently deprotononated by n-BuLi at e40 C in 1,2-dimethoxyethane (DME) and reacted with (CO) 5 MnBr. A significant change in colour of the reaction medium from light orange to dark red occurred when the temperature was raised to e20 C and stepwise brought to reflux.…”

“…In an experiment carried out with with a 2:1 ratio of 1.Li and (CO) 5 MnBr, the characterization of reaction intermediates was attempted. The reaction medium resulting from the addition of an excess of a DME solution of 1.Li to the manganese (I) substrate led to a deep red solution in 1,2-dimethoxyethane, the content of which was first analyzed by FT-IR spectroscopy and subsequently analyzed by 13 C NMR at room temperature upon replacement of the solvent by d 8 .THF.…”

“…In view of the experimental evidence gathered for the synthesis of 2 by reaction of 1.Li with (CO) 5 MnBr, various intermediates were envisaged and the mechanism of this reaction was sought considering the following elementary steps, which were deemed reasonable according to various reports dealing with similar Scheme 1. Reactions of ligand 1 with n-butyllithium and with (h 1 -benzyl) pentacarbonylmanganese.…”

“…provides the most direct leading thread: 1) the nucleophilic addition of 1.Li to a cis-carbonyl ligand of (CO) 5 …”

“…Three main routes to functionalized cymantrene derivatives from cyclopentadienyl-type ligands can be considered. The first is the reaction of cyclopentadienylides with (CO) 5 MnX (X ¼ halide) compounds that leads, via a multistep process, to a thermodynamically stable pentahapto cyclopentadienyl complex [8]. The second is the thermolytic reaction of diazocyclopentadienes with alkyl and aryl-manganesecarbonyl compounds, which entails the transient formation of carbene or carbenoid e type intermediates [12e15].…”