[reaction: see text] The viability of oximes as nucleophiles in transition-metal-catalyzed allylic substitution was examined. The oxygen atom of oxime acted as a reactive nucleophile in the reaction of a pi-allyl palladium complex. In the presence of Pd(PPh3)4, the allylic substitution of oximes with allylic carbonate afforded the linear O-allylated oxime ethers selectively without a base. In contrast, the palladium-catalyzed reaction with allylic acetate proceeded smoothly in the presence of K2CO3 or Et2Zn as a base. Selective formation of nitrones was achieved by using palladium(II) catalyst. In the presence of Pd(cod)Cl2, the allylic substitution of oximes with allylic acetate afforded the N-allylated nitrones under solvent-free conditions, as a result of the reaction with the nitrogen atom of oximes.
As a convenient and direct functionalization of guanidines, the transition metal-catalyzed allylic substitution of guanidines was studied. The guanidine derivatives bearing two electron-withdrawing substituents acted as reactive nucleophiles in the allylic substitution to give the monoallylated products. The double allylic substitution was achieved by using tri-Boc-guanidine bearing three electron-withdrawing substituents as a nucleophile to give the diallylated products. The regiocontrol in the allylic substitution of unsymmetrical allylic substrates has been investigated by employing the palladium or iridium catalysts. The iridium complex of chiral pybox ligand allowed the regio- and enantioselective allylic substitution. Asymmetric double allylic substitution of tri-Boc-guanidine with phosphate bearing the 1-naphthyl group gave the diallylated product with high diastereo-, regio-, and enantioselectivities.
Diastereo isomericerythro and threo forms of 2,3-epoxy-l-phenylphospholane 1-oxides were synthesized from threo and erythro forms of 2-bromo-3-hydroxy-l-phenylphospholane 1-oxides being prepared from l-phenyl-2-phospholene 1-oxide. Alternatively, the epoxides were also prepared by the epoxidation of the 2-phospholene with peroxides such as sodium peroxide and hydrogen peroxide. The reactivity and regioselectivity for the reaction of erythro and threo forms of the 2,3-epoxides with nucleophiles were investigated by using amines, and the reaction afforded 2-amino-3-hydroxy-l-phenylphospholane 1-oxides, which correspond to phospha sugar N-glycosides.2,3-Dibromo-3-methyl-l-phenylphospholane 1-oxides were first prepared from 3-methyl-l-phenyl-2-phospholene 1-oxide. The prepared phospholanes or phospha sugars were biologically qualified by ΜΤΓ(3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide) in vitro method to find that some of these phosphorus heterocycles or phospha sugars have quite efficient anti-cancer activity for leukemia cells in manners of (i) wide spectra, (ii) high activities, and (iii) high specificities.
The synthesis of the novel 1‐(substituted phenoxy/phenyl)‐2‐phospholene and phospholane 1‐oxide derivatives, which are analogs of sugars having a phosphorus atom in place of the ring oxygen of normal sugars, is described. All of the synthesized derivatives are structurally characterized by multi nuclear NMR, mass, and IR spectral data, elemental and X‐ray crystallographic analyses.
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