Nickel-catalysed substitution reactions of allylic carbonates with aryl- and alkenyl-borates

Abstract

Substitution reactions of 1,3-disubstituted allylic carbonates 3 with aryl-and alkenyl-borates 4 are catalysed by [NiC12(dppf)] [dppf = 1 ,I '-bis(diphenylphosphino)ferrocene], and in the case of the cyclic carbonate 7, the reaction proceeds with complete inversion.

Nickel-catalyzed allylic carbonylative coupling of alkyl zinc reagents with tert-butyl isocyanide

“…The stereochemistry of this carbonylative coupling reaction was also examined by using (R)-1af as the starting material (Fig. 6b): the desired product 4af was obtained with 75% ee (enantiomeric excess) with the inversed configuration, which indicated that the initiate step most likely undergo SN2 type in the oxidative addition process similar to the Tsuji-Trost-type oxidation [64][65][66] . The erosion of ee may arise from the tautomerization between imine and enamine intermediate in the acidic work up procedure.…”

Nickel‐Catalyzed Allylic Alkylation with Diarylmethane Pronucleophiles: Reaction Development and Mechanistic Insights

“…Thus expanding the scope of soft nucleophiles in palladium‐catalyzed AAAs has attracted attention . In contrast to palladium‐catalyzed allylic substitutions, which have been extensively used with soft nucleophiles, nickel catalysts have generally been paired with hard nucleophiles, such as Grignard reagents and other main‐group organometallics . An advantage of nickel catalysts over palladium is their lower cost.…”

Metal‐Catalyzed Cross‐Coupling Reactions of Organoboron Compounds with Organic Halides

“…On the other hand, ate-complexes of aryl-or 1-alkenylboronates such as 144 smoothly undergo cross-coupling in the absence of a base or reducing reagent. Reactions with iodo-or bromoalkenes [193,194], allyl acetates [195,196], and aryl mesylates [96] proceed smoothly at room temperature. The reaction of cyclic allyl carbonate (145) occurs with inversion of the stereochemistry via oxidative addition (with inversion) and arylation (from the same face of the nickel) [195].…”

“…Reactions with iodo-or bromoalkenes [193,194], allyl acetates [195,196], and aryl mesylates [96] proceed smoothly at room temperature. The reaction of cyclic allyl carbonate (145) occurs with inversion of the stereochemistry via oxidative addition (with inversion) and arylation (from the same face of the nickel) [195]. The oxidative addition of chloroarenes to nickel(0) complexes shows a Hammett correlation that is quite different from that of palladium(0) complexes (Scheme 2-28).…”

“…The observed selectivities suggest an addition-elimination mechanism involving the formation of Ar-Pd-OAc via transmetallation between Pd(OAc) 2 and ArB(OH) 2 , syn-addition to the glycal double bond and finally anti-elimination of Pd(OAc) 2 . This is in sharp contrast to the nickel-catalyzed arylation of cyclic allyl carbonates (145), which gives analogous inversion products via an oxidative addition-transmetallation process [195]. The aryl-benzyl coupling reaction provides a simple method for the synthesis of open-chained mixed calix[4]arene analogs (272) [386].…”