Selective Cross‐Coupling of Unsaturated Substrates on Al^I

Abstract

The Al I compound NacNacAl(1,N acNac = [ArNC-(Me)CHC(Me)NAr] À ,A r= 2,6-iPr 2 C 6 H 3)s erves as at emplate for the chemoselective coupling between carbonyls (benzophenone, fenchone, isophorone, p-tolyl benzoate, N,N-dimethylbenzamide, (1-phenylethylidene)aniline)a nd pyridine. With the CH-acidic ketone (1R)-(+ +)c amphor,t he reaction affords ah ydrido alkoxide compound of Al,f ormed as the result of enolization,w hereas an enolizable imine, (1-phenylethylidene)aniline, and the bulky ketone isophorone, still chemoselectively couple with pyridine. In contrast, reaction with the ester p-tolyl benzoate resultsi nc leavage of the ester bond together with replacement of the alkoxy group by ah ydrogen atom of the pyridine moiety.T his study demonstrates that for carbonyl substrates featuring phenyls ubstituents, the reaction proceeds via intermediate formation of h 2 (C,X)-coordinated (X = O, N) carbonyl adducts,w hereas the reactiono f1 with (R)-(À)-fenchone in the absence of pyridine leads to CH activation in the pendant isopropyl group of the Ar substituent of the NacNacl igand.

Hydrocarbon Soluble Alkali‐Metal‐Aluminium Hydride Surrog[ATES]

“…The alternating arrangement of short and long bond lengths within C6−C7−C8−C9−N1 (Figure 2 ‐bottom‐B) confirms the presence of conjugation in the t BuDHP ring. However, upon comparing the absolute values of the bond parameters we find a close resemblance to β‐diketiminate stabilized 1,2‐dihydropyridylaluminium systems[ 16a , 16b ] rather than the monometallic lithium analogues [7b] (Figure 2 ‐bottom). This indicates the preferential bias of the t BuDHP nitrogen atom towards sharing its electron density with the neighbouring aluminium centre.…”

Incorporating Trimethylaluminium into the Structures of Alkali Metal (Li, Na, K, Cs) dihydropyridines

“…Incorporating trimethylaluminium into the structures of alkali metal (Li, Na, K, Cs) dihydropyridines Al-Cbridging [1.983(7)-2.013(3) Å] and Al-N [1.920(4)-1.941( 1) Å] bond distances regardless of alkalimetal identity. These Al-N distances are longer than those seen in Nikonov's recent series of neutral Al-DHP complexes [1.815(5)-1.839( 2) Å] [16] on account of having four anionic ligands rather than three, and are more in line with the related AM(tBuDHP)Al(TMP)iBu2 complexes [1.937(2)-1.986( 2) Å] which have a similar arrangement. [8] The Al-DHP relationship also differs from that in AM(tBuDHP)AlMe3 on The AM-NDHP distances are longer than the dative AM-Ndonor distances in each complex 1-4, suggesting that there is little interaction between the alkali-metal and the formally amido (DHP) anion.…”

“…The Me 3 Al( t BuDHP) units display a narrow range of Al−C terminal [1.989(4)‐2.004(4) Å], Al−C bridging [1.983(7)‐2.013(3) Å] and Al−N [1.920(4)‐1.941(1) Å] bond distances regardless of alkali‐metal identity. These Al−N distances are longer than those seen in Nikonov's recent series of neutral Al−DHP complexes [1.815(5)‐1.839(2) Å] [16] on account of having four anionic ligands rather than three, and are more in line with the related AM( t BuDHP)Al(TMP) i Bu 2 complexes [1.937(2)‐1.986(2) Å] which have a similar arrangement [8] . The Al−DHP relationship also differs from that in AM( t BuDHP)Al(TMP) i Bu 2 on account of the poorer bridging ability of the Me group ( vide infra ) in comparison to the bridging TMP groups.…”

Ketyl Radicals Generated from Magnesium(I) Compounds: Useful Reagents for C−C Bond Forming Reactions

“…This seemed all the more timely, considering that Nikonov and co-workers reported that a aluminium(I) compound, [( Dip Nacnac)Al:] can similarly reductively couple benzophenone with N-aromatics, though seemingly not via ketyl intermediates. [26] Toluene solutions of [{( Mes Nacnac)Mg} 2 ] [27] were treated with mixtures of two equivalents of both phenanthroline and one of the ketones, benzophenone, 2-methylbenzophenone or 9xanthenone. In each case there was an immediate change of color of the solution to purple or deep-blue, indicating the formation of a magnesium ketyl complex.…”