Enantioselective and regiodivergent allylation of pyrimidines with terminal allenes: an approach to pyrimidine acyclic nucleosides†
An atom-economic addition of pyrimidines to allenes has been developed for the diverse synthesis of branched or linear N-allylpyrimidine analogues. With [Rh(COD)Cl]2/chiral MeOBIPHEP as the catalyst, the asymmetric allylation reaction proceeded well and afforded the branch selective adducts in good yields, with high regio- and enantioselectivities. Meanwhile, when [Pd(η3-allyl)Cl]2/DPPF was used as the catalyst, the linear-selective allylation of pyrimidines could be carried out in good yields. Here, the configuration of the CC bond in the side chain of the products was mainly found to be the E-form.