Efficient methods to prepare enantiopure 1,2-oxazin-4-yl nonaflates and phosphates were elaborated. The corresponding 1,2-oxazin-4-ones were transformed into their enolates and then quenched with nonafluorobutanesulfonyl fluoride or diphenyl chlorophosphate to provide the title compounds. Alternatively, the corresponding α-bromo ketones were subjected to Perkow reactions efficiently leading to the respective enol phosphates. A variety of palladium-catalyzed cross-couplings such as Kumada-Corriu, Sonogashira, Heck reactions or borylation reactions were studied, which delivered the expected new 4-substituted 1,2-oxazine derivatives generally in satisfactory yields. A few typical subsequent transformations were studied including a copper-catalyzed [3+2] cycloaddition with a galactose-derived azide. They demonstrate the synthetic potential of the newly prepared enantiopure 4-substituted 1,2-oxazines.

In addition to the transformation of the prepared 1,2‐diketones into quinoxalines, their conversion into imidazole, thiophene and 4‐oxoalk‐2‐enoate derivatives is described.

The nonaflate (III) is prepared from the corresponding ketone (I) and converted into various 4‐substituted derivatives by Kumada‐Corriu, Sonogashira, Heck‐ or borylation reactions.

The deprotonation of 3-aryl-substituted alkyl propargyl ethers with n-butyllithium provides an ambident anion that reacts with carbonyl compounds to provide mixtures of γ-substituted products with alkoxyallene substructure and of α-substituted propargyl ethers. The ratio of the two product types strongly depends on the solvent: in diethyl ether the γ-substituted products predominate whereas the more polar tetrahydrofuran favors the α-adducts. The primary addition products undergo 5-endo-trig or 5-endo-dig cyclizations under various reaction conditions to afford isomeric furan derivatives. The highest selectivity in favor of α-substituted products was achieved by employing a MOM-protected propargyl ether. During the protonation step no evidence for a proton shift leading to an isomeric allenyl anion was found. A brief mechanistic discussion tries to rationalize the observed regio­selectivities.

Synthesis and NMR spectroscopic data of starting materials page 2-5 References page 5 Copies of spectra page 6-20 General Information: Reactions were generally performed under argon in flame-dried flasks. Solvents and reagents were added by syringes. Solvents were dried using standard procedures. Reagents were purchased and were used as received without further purification unless stated. Reactions were monitored by thin-layer chromatography (TLC). Products were purified by column chromatography on silica gel (32-63 μm). Unless otherwise stated, yields refer to chromatographically homogeneous and spectroscopically pure materials (1 H-NMR spectroscopy). NMR spectra were recorded with JEOL (ECX 400, Eclipse 500) instruments. Chemical shifts are reported relative to TMS (1 H: δ = 0.00 ppm) and CDCl3 (13 C: δ = 77.0 ppm). Integrals are in accordance with assignments; coupling constants are given in Hz. 13 C-NMR spectra are 1 H-decoupled. Multiplicity is indicated as follows: s (singlet), d (doublet), t (triplet),