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Arylacetylenes undergo anti‐1,2‐dizincation to afford trans‐1,2‐dizincioalkenes. The process employs sodium dispersion as a reducing agent and zinc chloride TMEDA complex as a reduction‐resistant zinc electrophile. This reductive anti‐dizincation contrasts with the conventional additive syn‐dimetalation like silylzincation. The resulting dizincated alkenes undergo the cross‐coupling to yield multi‐substituted alkenes stereoselectively. [ABSTRACT FROM AUTHOR]

In contrast to the well‐established oxidative C=C double bond cleavage to give the corresponding carbonyl compounds, little is known about reductive C=C double bond cleavage. Here we report that C−C single bond cleavage in 1,2‐diaryl‐1,2‐diborylethanes proceeds by reduction with sodium metal to yield α‐boryl benzylsodium species. In combination with our previous reductive diboration of stilbenes, the overall transformation represents reductive cleavage of the C=C double bonds of stilbene to yield α‐boryl‐α‐sodiated toluenes. This reductive two‐step C=C double bond cleavage is applicable to ring‐opening or ring‐expansion reactions of polycyclic aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

The article titled "Front Cover: Reductive anti‐Dizincation of Arylacetylenes" discusses a new method for achieving anti‐1,2‐dizincation of arylacetylenes. This process involves electron injection using sodium dispersion and transmetalation with a zinc chloride TMEDA complex. The resulting dizincated alkenes can then undergo the Negishi cross‐coupling to produce multi‐substituted alkenes with high stereoselectivity. This research provides a novel approach for the anti‐selective diarylation of alkynes. The article provides more detailed information on this topic. [Extracted from the article]

A sterically encumbering multidentate β‐diketiminato ligand, tBuL2 (tBuL2=[ArNC(tBu)CHC(tBu)NCH2CH2N(Me)CH2CH2NMe2]−, Ar=2,6‐iPr2C6H3), is reported in this study along with its coordination chemistry to zirconium(IV). Using the lithio salt of this ligand, Li(tBuL2) (4), the zirconium(IV) precursor (tBuL2)ZrCl3 (6) could be readily prepared in 85 % yield and structurally characterized. Reduction of 6 with 2 equiv of KC8 resulted in formation of the terminal and mononuclear zirconium imide‐chloride [C(tBu)CHC(tBu)NCH2CH2N(Me)CH2CH2NMe2]Zr(=NAr)(Cl) (7) as the result of reductive C=N cleavage of the imino fragment in the multidentate ligand tBuL2 by an elusive ZrII species (tBuL2)ZrCl (A). The azabutadienyl ligand in 7 can be further reduced by 2 e− with KC8 to afford the anionic imide [K(THF)2]{[CH(tBu)CHC(tBu)NCH2CH2N(Me)CH2CH2N(Me)CH2]Zr=NAr} (8‐2THF) in 42 % isolated yield. Complex 8‐2THF results from the oxidative addition of an amine C−H bond followed by migration to the vinylic group of the formal [C(tBu)CHC(tBu)NCH2CH2N(Me)CH2CH2NMe2]− ligand in 7. All halides in 6 can be replaced with azides to afford (tBuL2)Zr(N3)3 (9) which was structurally characterized, and reduction with two equiv of KC8 also results in C=N bond cleavage of tBuL2 to form [C(tBu)CHC(tBu)NCH2CH2N(Me)CH2CH2NMe2]Zr(=NAr)(N3) (10), instead of the expected azide disproportionation to N3− and N2. Solid‐state single crystal structural studies confirm the formation of mononuclear and terminal zirconium imido groups in 7, 8‐Et2O, and 10 with Zr=NAr distances being 1.8776(10), 1.9505(15), and 1.881(3) Å, respectively. [ABSTRACT FROM AUTHOR]