Activated Metallic Nickel in the Preparation of Symmetrical 1,3-Diarylpropan-2-Ones From Benzylic Halides and Alkyl Oxalyl Chlorides

Abstract

Carbonylation with group VIII transition metal complexes has been shown to be a powerful tool in organic synthesis because it is easy to undergo oxidative addition of organic halides to transition metals and insertion of carbon monoxide to organotransition metals formed.') Metal carbonyls such as diiron nonacarbonyl,2-4) triiron dodecacarbonyl,4'S) nickel carbonyl,6'7) and dicobalt octacarbonyl8) have been employed for the preparation of symmetrical ketones from aryl, benzyl, and arylmercuric halides9) in a stoichiometric fashion.10) Disodium tetracarbonylferrate4,11) or potassium hexacyanodinickelate-carbon monoxide 12) have also been used for dibenzyl ketone synthesis.In spite of usefulness of these complexes, it is generally not possible to cause the satisfactory reaction with transition metals in the metallic state 13) under mild conditions due to their poor reactivity. In a previous communication we reported that activated metallic nickel, prepared by the reduction of nickel halide with lithium, underwent oxidative addition of benzylic halides to give homo-coupled products. 14) We now report that carbonylation of the oxidative adducts of benzylic halides to the nickel proceeded smoothly to afford symmetrical 1,3-diarylpropan-2-ones in moderate yields, in which the carbonyl groups of alkyl oxalyl chlorides served as a source of carbon monoxide.Metallic nickel was prepared in glyme (25 ml) by the reduction of nickel iodide (3.13 g, 10 mmol) with lithium (0.160 g, 23 mmol) using naphthalene (0.128 g, 1 mmol) as an electron carrier.

Stoichiometric Reactions of Acylnickel(II) Complexes with Electrophiles and the Catalytic Synthesis of Ketones

“…Stoichiometric reactions with Ni­(CO) 4 with electrophiles to form ketones are well-known to proceed via intermediate acylnickel­(II) complexes (eq ), but these reactions are not often used today due to toxicity concerns and limited availability. , Catalytic versions of these stoichiometric reactions have proven to be difficult to develop. …”