Preparation of (Z)-1-fluoro-1-alkenyl carboxylates,carbonates and carbamates through chromium mediated transformation of dibromofluoromethylcarbinyl esters and the reactivity as double acyl group donors

CrCl₂/Mn-mediated transformation of various dibromofluoromethylcarbinyl esters including carboxylates, carbonates and carbamates provided 1-fluoro-1-alkenyl esters via [2,3]-sigmatropic rearrangement of ester group. Reaction proceeded by using CrCl₂/Mn system under mild conditions (in THF at room temperature) to give 1-fluoro-1-alkenyl esters in good yield with an excellent Z selective manner. 1-Fluoro-1-alkenyl ester thus obtained acts as a double acyl donor in the reaction with necleophiles such as amine, thiol, alcohol as well as bifunctional necleophiles such as ethylene diamine derivative.     

The stereochemical investigation of 3-Aryl-4-methyl-1,2,3-oxathiazolidine 2-oxides using NMR

The title compounds were prepared by the reaction of the corresponding N-2-hydroxyisopropylanilines with thionyl chloride in the presence of triethylamine, and their pmr and cmr spectra were examined. On the basis of the chemical shifts due to the γ- and δ-effects, the stereochemical structures are discussed.     

Synthesis of 4,8-dimethyl-6-phenyl-5,6,7,8-tetrahydro-4H-1,3,6-dioxazocines

Five 6-phenyl-5,6,7,8-tetrahydro-4H-1,3,6-dioxazocines were synthesized by the reaction of the corresponding N,N-bis(2-hydroxypropyl)- and N,N-bis(2-hydroxyethyl)chloroanilines with paraformaldehyde in the presence of p-toluenesulfonic acid.     

Relationship Between the J(Sn–C–H) of the Dimethyltin Dichloride Adducts of some Pyridines and Anilines,and the Donor Strength of the Lewis Bases

A study by titrimetric methods of the donor strength of pyridine and aniline and some of their para -substituted derivatives, and the J (¹¹⁹Sn–C–H) of their adducts with dimethyltin dichloride in nitrobenzene, has shown that the p K _b of a Lewis base and its para -substituted derivatives varies linearly with the J (¹¹⁹Sn–C–H) of the adducts of dimethyltin dichloride (Me₂SnCl₂), with the Lewis base dissolved in an inert solvent. A graphical plot of the p K _b of a given series of Lewis bases versus the J (Sn–C–H) of their complexes with Me₂SnCl₂ in nitrobenzene (at the same temperature, and same complex concentration) gives a straight line with a negative gradient, making possible the deduction of the other parameter (e.g. p K _b) for a Lewis base in the series, where the one parameter (e.g. J (Sn–C–H) is known. The graph for each series of Lewis base has its own characteristic gradient, and the gradients appear proportional in magnitude to the donor strengths of each class of the bases, making it possible to deduce from such graphs which series of Lewis bases are the stronger donors.     

Cis and trans 4,8-dimethyl-6-phenyl-5,6,7,8-tetra-hydro-4H-1,3,6-oxadiazocin-2-ones: Conformational studies and configurational assignments by NMR

The reaction of N-(2-aminopropyl)-N-(2-hydroxypropyl)aniline with phosgene afforded cis and trans isomers of 4,8-dimethyl-6-phenyl-5,6,7,8-tetrahydro-4H-1,3,6-oxadiazocin-2-one. On the basis of ASIS data and Eu-shift difference, the title compounds are found to exist as boat-chair conformation in which the carbonyl carbon resides at the BC-2 position on the molecular plane.     

The stereochemistry of 4,8-dimethyl-6-phenyl-5,6,7,8-tetrahydro-4H-1,3,6-dioxazocin-2-ones using NMR

Two isomeric 4,8-dimethyl-6-phenyl-5,6,7,8-tetrahydro-4H-1,3,6-dioxazocin-2-ones were prepared, and their pmr and cmr spectra were examined. From the tris(dipivaloylmethanato) europium (Eu(dpm)₃) shift reagent and the dihedral angle, the title compounds are found to exist in the eq-ax and eq-eq methyl groups with boat-chair form.     

Isolation and Structure Determination of a Missing Endohedral Fullerene La@C70 through In Situ Trifluoromethylation

D_5h‐symmetric fullerene C₇₀ (D_5h‐C₇₀) is one of the most abundant members of the fullerene family. One longstanding mystery in the field of fullerene chemistry is whether D_5h‐C₇₀ is capable of accommodating a rare‐earth metal atom to form an endohedral metallofullerene M@D_5h‐C₇₀, which would be expected to show novel electronic properties. The molecular structure of La@C₇₀ remains unresolved since its discovery three decades ago because of its extremely high instability under ambient conditions and insolubility in organic solvents. Herein, we report the single‐crystal X‐ray structure of La@C₇₀(CF₃)₃, which was obtained through in situ exohedral functionalization by means of trifluoromethylation. The X‐ray crystallographic study reveals that La@C₇₀(CF₃)₃ is the first example of an endohedral rare‐earth fullerene based on D_5h‐C₇₀. The dramatically enhanced stability of La@C₇₀(CF₃)₃ compared to La@C₇₀ can be ascribed to trifluoromethylation‐induced bandgap enlargement.