Tomoyasu Iwaoka

A novel enantioselective preparation of α-fluoro-β-keto acids☆

Abstract A two-step method for the enantioselective preparation of α-fluorinated β-keto acids from 1,3-dioxin-4-ones having l-menthone as the chiral auxiliary at the 2-position is described. The method consists of fluorination of the dioxinones by molecular fluorine and solvolytic cleavage of the acetal function.

Chiral 2-vinyl-1,3,2-oxazaphospholidin-2-ones: new dienophiles for asymmetric Diels–Alder reactions

Diels–Alder reactions of chiral dienophiles: (2R,4S)- and (2R,4S)-2-vinyl-1,3,2-oxazaphospholidin-2-ones (3 and 4) derived from (S)-valinol with cyclopentadiene led to mixtures of endo- and exo-adducts with high diastereofacial selectivity (>90% for 3 and 80 and 88% respectively for 4); an explanation is proposed based on X-ray crystallographic structures for the dienophile and the derived endo-cycloadduct 5.

Use of 1,3-dioxin-4-ones and related compounds in synthesis. Part 37. 5-Trifluoromethyl-1,3-dioxin-4-ones as versatile building blocks for trifluoromethylated aliphatic compounds

Synthesis of 5-trifluoromethyl-1,3-dioxin-4-ones and their use for the preparation of a variety of trifluoromethylated aliphatic compounds are described. Their usefulness has been demonstrated either by the formation of α-trifluoromethyl-β-keto esters via the corresponding acylketenes or by their direct participation in pericyclic reactions as a π2 component.

Synthesis of 5-fluoro-1,3-dioxin-4-ones: versatile building blocks of fluorinated compounds

Fluorination of 5,6-unsubstituted 1,3-dioxin-4-ones by fluorine followed by treatment with triethylamine affords the title compounds, which can be converted into fluorinated derivatives of either formylacetic acid or of heterocyclic systems.

Synthesis of 1,3-dioxin-4-ones having a trifluoromethyl group at the 5-position: versatile building blocks for trifluoromethylated compounds

The reaction of 5-iodo-1,3-dioxin-4-ones with trifluoromethyl iodide in the presence of copper powder in hexamethylphosphoric triamide affords the title compounds, which can be converted either to α-trifluoromethylated β-keto acid derivatives or to uracil or oxazine derivatives bearing a trifluoromethyl group.