Multiple Cycloaddition Reactions of Ketones with a β‐Diketiminate Al Compound

Abstract

A β-diketiminate Al compound (1) with an exocyclic double bond reacts with two equivalents each of benzophenone and 2-benzoylpyridine in a [4+2] cycloaddition to generate bicyclic and tricyclic compounds 2 and 3, respectively. Compound 2 consists of six- and eight-membered aluminium rings, whereas 3 has two five- and one eight-membered ring. Compounds 2 and 3 were characterized by a number of analytical tools including single-crystal X-ray diffraction. The quantum mechanical calculations suggest that the dissociation of the solvent molecule from 1 would lead to an active species 1A having two 1,4-dipolar 4π electron moieties, in which the electrophilic site is the Al atom and the nucleophilic positions are polarized exocyclic and endocyclic C=C π bonds. The detailed mechanistic study shows that the dipolarophiles, benzophenone, and 2-benzoylpyridine undergo double cycloaddition with two 1,4-dipolar 4π electron moieties of 1A. Herein, the addition of one molecule of the dipolarophile promotes the addition of the second one.

On the non-innocence of “Nacnacs”: ligand-based reactivity in β-diketiminate supported coordination compounds

“…241 Even if (#BDI*)Ge does not react with H 2 , it is hydrogenated with ammonia-borane leading to the formation of (BDI*)GeH in which the BDI ligand is restored (Scheme 71bottom). 143 Overall these results highlight the dipolar character of Zwitterionic (#BDI) coordination compounds and their interest for cooperative metal-ligand bond activation. 276 leads to novel samarium amides bearing entirely modified β-diketiminato ligands as depicted on Scheme 72.…”

“…As already discussed, multiple additions of ketones to the γ-C and β-CH 2 groups in (#BDI*)AlMe(THF) were also reported recently (Scheme 32). 143 Overall these results highlight the dipolar character of Zwitterionic (#BDI) coordination compounds and their interest for cooperative metal-ligand bond activation.…”

“…139 Similarly, (BDI*)PbF reacts with the activated ketone F 3 C(CO)Ph to form a homoleptic lead compound in which the ketone is incorporated at the ligand. 143 The sensitivity of the BDI γ-carbon towards electrophilic attack is also critical in the presence of nitriles. 142 Multiple cycloaddition reactions of ketones at the γ-C and β-CH 2 positions of (#BDI*)AlMe(THF) that generate bicyclic and tricyclic compounds represented on Scheme 32 were also reported recently.…”

“…142 Multiple cycloaddition reactions of ketones at the γ-C and β-CH 2 positions of (#BDI*)AlMe(THF) that generate bicyclic and tricyclic compounds represented on Scheme 32 were also reported recently. 143 The sensitivity of the BDI γ-carbon towards electrophilic attack is also critical in the presence of nitriles. Several studies report C-C coupling reactions between the nitrile carbon and the methylene carbon of β-diimine ligands in the presence of bases, which involve BDI intermediates (Scheme 33top).…”

Element‐Ligand Cooperativity with p‐Block Elements

“…Deprotonation of one of the methyl groups of the β‐diketiminato ligand in 23 gave neutral Al(III) complex 27 (Figure d). The AlLC reactivity of 27 toward carbonyl compounds was investigated by the Roesky, Schulzke, and the Parameswaran group . 27 reacted in a stepwise manner with two equivalents of benzophenone or 2‐benzoylpyridine.…”