12117-34-9

Upstream product

• 613-33-2 (4,4'-dimethyl-1,1'-biphenyl) 
• 199620-14-9 chromium⁽⁰⁾ hexacarbonyl 

Downstream Products

• 1350563-76-6 (CH₃C₆H₄C₆H₄CH₂C₆H₉)Cr(CO)3 

Relevant academic research and scientific papers

Mechanistic aspects of the reactions of bis(tricarbonylchromium) coordinated biphenyl dianions with electrophiles and their subsequent oxidation

Reaction of the (η6:η6-biphenyl)bis(tricarbonylchromium) dianion (2) with a wide variety of primary electrophiles results exclusively in an ipso addition. NMR data point out the formation of the endo isomer upon protonation. While a definitive answer is not possible for primary alkyl electrophiles, indirect evidence suggests either a carbanionic type SN2 or a metal-assisted endo addition to the ipso position. Reaction with cyclopropylcarbinyl bromide as well as 6-bromo-1-hexene suggests an inner-sphere polar SN2 mechanism for most of the primary electrophiles. However, easily reduced halides such as allylic and benzylic or those halides which have steric hindrance toward SN2 processes may well proceed via an electron-transfer process or a combination of SN2 and electron-transfer processes. 1,2-Aryl migration has been found to be the predominant pathway in the oxidative cleavage of the alkylated (η6:η 6-4,4′-dimethylbiphenyl)bis(tri-carbonylchromium) dianion (6), thereby indicating a cationic intermediate in the mechanism of this step. Alkylation followed by iodine oxidation of 4,4′-disubstituted biphenyls provides a short convenient approach to 2-alkyl-5,4′-disubstituted biphenyls.

Palladium-catalyzed allylic substitution with (η6-Arene- CH2Z)Cr(CO)3-based nucleophiles

Although the palladium-catalyzed Tsuji-Trost allylic substitution reaction has been intensively studied, there is a lack of general methods to employ simple benzylic nucleophiles. Such a method would facilitate access to "α-2-propenyl benzyl" motifs, which are common structural motifs in bioactive compounds and natural products. We report herein the palladium-catalyzed allylation reaction of toluene-derived pronucleophiles activated by tricarbonylchromium. A variety of cyclic and acyclic allylic electrophiles can be employed with in situ generated (η6-C 6H5CHLiR)Cr(CO)3 nucleophiles. Catalyst identification was performed by high throughput experimentation (HTE) and led to the Xantphos/palladium hit, which proved to be a general catalyst for this class of reactions. In addition to η6-toluene complexes, benzyl amine and ether derivatives (η6-C6H5CH 2Z)Cr(CO)3 (Z = NR2, OR) are also viable pronucleophiles, allowing C-C bond-formation α to heteroatoms with excellent yields. Finally, a tandem allylic substitution/demetalation procedure is described that affords the corresponding metal-free allylic substitution products. This method will be a valuable complement to the existing arsenal of nucleophiles with applications in allylic substitution reactions.