Allyl amides , oxazoline synthesis

Kang and co-workers prepared the (3-halo amide arrangement required for oxazoline formation from allylic alcohols via a two-step process. For example, treatment of the allylic alcohol 122 with trichloroacetonitrile and base followed by activation of the double bond with iodine monochloride, provides 123. Hydrolysis of 123 gave 124 from which cyclization provided the oxazoline 18a used for paclitaxel synthesis (Scheme 8.36). 

A wide number of chiral palladium complexes have been used in the context of DKR. In 1999, Cook et al. reported the palladium-mediated synthesis of chiral vicinal diamines from chiral oxazolidinones. The process involved successive oxidative insertion, loss of CO2 and subsequent cyclisation at the amide oxygen atom. The intermediate re-allyl palladium complexes underwent a rapid equilibration. Moreover, the intermediate oxazoline was also ionised by the palladium catalyst and was in equilibrium with the 7t-allylpalladium complexes, giving rise to thermodynamically controlled product ratios. These dynamic intermediates could be trapped with phthalimide under kinetic control to afford enantio- and diastereoselectively the corresponding syn-ch x 1,2-diamines (Scheme 2.46). 

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