This mini-review describes the scope of the halogen-magnesium exchange. It shows that the use of turbo-Grignard reagent (iPrMgCl·LiCl) greatly enhances the rate of the Br- and I-Mg exchange. Furthermore, this magnesium reagent allows the performance of a fast sulfoxide-magnesium exchange. Also, the use of sBuMgOR·LiOR (R = 2-ethylhexyl) enables a Br/Mg-exchange in toluene leading to various Grignard reagents in toluene. Additionally, the new exchange reagent sBu₂Mg·2LiOR (R = 2-ethylhexyl) further increases the rate of the halogen-magnesium exchange allowing to perform a chlorine-magnesium exchange for aromatic chlorides bearing an ortho-methoxy substituent in toluene.
Organomagnesium compounds (Grignard reagents) are among the most useful organometallic reagents and have greatly accelerated the advancement of synthetic chemistry and related sciences. Nevertheless, heavy Grignard reagents based on the metals calcium, strontium or barium are not widely used, mainly due to their rather inert heavy alkaline-earth metals and extremely high reactivity of their corresponding Grignard-type reagents. Here we report the generation and reaction chemistry of butadienyl heavy Grignard reagents whose extremely high reactivity is successfully tamed. Facile synthesis of perfluoro-π-extended pentalene and naphthalene derivatives is realized by the in situ generated heavy Grignard reagents via intramolecular C-F/C-H bond cleavage. These obtained perfluorodibenzopentalene and perfluorodinaphthopentalene derivatives show low-lying LUMO levels, with one being the lowest value so far among all pentalene derivatives. Our results set an exciting example for the meaningful synthetic application of heavy Grignard reagents.
Avariety of functionalizedt riarylmethane and 1,1diarylalkane derivatives were prepared via at ransition-metalfree,one-pot and two-step procedure,involving the reaction of various benzal diacetates with organozinc reagents.Asequential cross-coupling is enabled by changing the solvent from THF to toluene,a nd at wo-step S N 1-type mechanism was proposed and evidenced by experimental studies.The synthetic utility of the method is further demonstrated by the synthesis of several biologically relevant molecules,s uch as an anti-tuberculosis agent, an anti-breast cancer agent, ap recursor of as phingosine-1-phosphate (S1P) receptor modulator,a nd aFLAP inhibitor. Scheme 1. Typical methods for the synthesis of triarylmethanes and 1,1-diarylalkanes.
Transmetalation of 1,4‐dilithio‐1,3‐butadienes with Ba[N(SiMe3)2]2 gave barium dibenzopentalenides, which were structurally characterized by single‐crystal X‐ray analysis. A preliminary study of the reaction chemistry of thus obtained barium dibenzopentalenides demonstrated that synthetically useful applications can be expected.
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