Awide range of polyfunctional diaryl-and diheteroarylzinc species were prepared in toluene within 10 min to 5h through an I/Zn or Br/Zn exchange reaction using bimetallic reagents of the general formula R' 2 Zn·2 LiOR (R' = sBu, tBu, pTol). Highly sensitive functional groups,s uch as at riazine, aketone,analdehyde,oranitro group,were tolerated in these exchange reactions,e nabling the synthesis of ap lethora of functionalized( hetero)arenes after quenching with various electrophiles.I nsight into the constitution and reactivity of these bimetallic mixtures revealed the formation of highly active lithium diorganodialkoxyzincates of type [R' 2 Zn-(OR) 2 Li 2 ].Organozinc reagents are key intermediates in organic synthesis as they tolerate many functional groups and readily participate in transition-metal-catalyzed carbon-carbon bond-forming reactions. [1] Aryl-and heteroarylzinc halides have been particularly widely used as organometallic reagents for preparing complex organic molecules. [2] Tw or ecently developed alternative synthetic strategies granting access to these valuable organometallics are the direct insertion of zinc powder into organic halides [3] and deprotonative metalation using TMP-zinc bases (TMP = 2,2,6,6-tetramethylpiperidyl). [4] Lithium alkylzincates such as "lower-order" R 3 ZnLi and "higher-order" R 4 ZnLi 2 have been shown to be able to promote halogen/zinc exchange reactions towards aryl halides. [5] Furthermore,anI/Zn exchange of aryl and heteroaryl iodides can be accomplished by adding substoichiometric amounts of Li(acac) to iPr 2 Zn in NMP. [6] Contrasting with the enhanced reactivity of these mixed-metal combinations, monometallic R 2 Zn reagents on their own fail to promote these type of transformations.Forp reparing related organomagnesium derivatives,t he exchange reagent iPrMgCl·LiCl ("turbo-Grignard") has been extensively used and leads to high rates of Br/Mg exchange. [7] This exchange can be accelerated further by replacing LiCl with as tronger donor additive,n amely al ithium alkoxide (ROLi;R= 2-ethylhexyl). Furthermore,t his exchange could be performed in the industrially friendly solvent toluene. [8] Opening new ground in this evolving area, we herein report an ew I/Zn and Br/Zn exchange in toluene based on the use of anovel bimetallic combination sBu 2 Zn·2 LiOR (1), which allows the generation of awide range of polyfunctional aryl-and heteroarylzinc reagents from the corresponding organic iodides or bromides.First, Et 2 Zn reacted in toluene with two equivalents of avariety of alcohols ROH(25 8 8C, 4h), affording the relevant ethylzinc alkoxides co-complexed with the corresponding alcohol (ROZnEt·ROH) of type 2. [9] These ethylzinc alkoxides (2)further reacted with sBuLi (2.0 equiv,inc yclohexane) to produce the bimetallic reagent tentatively represented as the trinuclear monozinc-dilithium complexes sBu 2 Zn·2 LiOR (1,s ee below). Removal of the solvents and subsequent redissolution in toluene provided al ight yellow solution of 1 (c = 0.6-1.0 m in toluene;S cheme 1), ...

While it is known that the addition of Group 1 alkoxides to s‐block organometallics can have an activating effect on reactivity, the exact nature of this effect is not that well understood. Here we describe the activation of sBu2Mg towards substituted bromoarenes by adding one equivalent of LiOR (R=2‐ethylhexyl), where unusually both sBu groups can undergo efficient Br/Mg exchange. Depending on the substitution pattern on the bromoarene two different types of organometallic intermediates have been isolated, either a mixed aryl/alkoxide [{LiMg(2‐FG‐C6H4)2(OR)}2] (FG=OMe; NMe2) or a homoaryl [(THF)4Li2Mg(4‐FG‐C6H4)4] (FG=OMe, F). Detailed NMR spectroscopic studies have revealed that these exchange reactions and the formation of their intermediates are controlled by a new type of bimetallic Schlenk‐type equilibrium between heteroleptic [LiMgsBu2(OR)], alkyl rich [Li2MgsBu4] and Mg(OR)2, with [Li2MgsBu4] being the active species performing the Br/Mg exchange process.

Using 2-methyl THF as solvent enables efficient and ultrafast amidation of esters by lithium amides at room temperature in air, edging closer towards reaching air- and moisture-compatible polar organometallic chemistry.

Using the bimetallic combination sBu 2 Mg•2 LiOR (R = 2-ethylhexyl) in toluene enables efficient and regioselective Br/Mg exchanges with various dibromo-arenes and -heteroarenes under mild reaction conditions and provides bromo-substituted magnesium reagents. Assessing the role of Lewis donor additives in these reactions revealed that N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDTA) finely tunes the regioselectivity of the Br/Mg exchange on dibromo-pyridines and quinolines. Combining spectroscopic with X-ray crystallographic studies, light has been shed on the mixed Li/Mg constitution of the organometallic intermediates accomplishing these transformations. These systems reacted effectively with a broad range of electrophiles, including allyl bromides, ketones, aldehydes, and Weinreb amides in good yields.

Though LiTMP (TMP=2,2′,6,6′‐tetramethylpiperidide) is a commonly used amide, surprisingly the heavier NaTMP has hardly been utilised. Here, by mixing NaTMP with tridentate donor PMDETA (N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine), we provide structural, and mechanistic insights into the sodiation of non‐activated arenes (e.g. anisole and benzene). While these reactions are low yielding, adding B(OiPr)3 has a profound effect, not only by intercepting the CAr‐Na bond, but also by driving the metalation reaction towards quantitative formation of more stabilized sodium aryl boronates. Demonstrating its metalating power, regioselective C2‐metalation/borylation of naphthalene has been accomplished contrasting with single‐metal based protocols which are unselective and low yielding. Extension to other arenes allows for in situ generation of aryl boronates which can then directly engage in Suzuki–Miyaura couplings, furnishing a range of biaryls in a selective and efficient manner.