(2S)-2-[(2S*,5R*,6R*)-5,6-Dimeth-oxy-5,6-dimethyl-1,4-dioxan-2-yl]-1-[(S)-1,1-dimethyl-ethylsulfon-yl]aziridine.

The reaction of a sulfur ylide with a chiral non-racemic sulfinyl imine afforded the desired aziridine in excellent yield and subsequent oxidation of the sulfinyl moiety dissolved in anhydrous dichloro-methane using a 75% aqueous solution of 3-chloro-per-oxy-benzoic acid afforded the title compound, C(14)H(27)NO(6)S. The configuration of the newly formed stereogenic center at the point of attachment of the 1,4-dioxane ring to the aziridine ring is S. The configurations of the pre-existing sites 2-, 5-, and 6-positions of the 1,4-dioxane ring prior to reaction of sulfinyl imine with the sulfur ylide are S, R, and R, respectively. The C-N bond lengths of the aziridine are 1.478 (2) and 1.486 (2) Å.

Sulfenylation Chemistry using Polymer-Supported Sulfides.

Clean sulfenylations are observed upon reaction of activated methylenes with phenyl succinimidyl sulfide. When working with diethyl benzylmalonate, the sulfenylated product can be selectively oxidized and thermally fragmented affording phenylsulfenic acid, initially, and diethyl benzylidenemalonate. The developed method was applied using a polymer-supported thioanisole derivative (JandaJel). Formation of the enedicarboxylate documents proof of principle of polymer-supported sulfides as sulfenylating agents onto activated methylenes.

Highly stereoselective methylene transfers onto butanediacetal-protected chiral non-racemic sulfinyl imines using S-ylide technology.

Diastereomeric ratios of >95 : 5 were obtained when performing methylene transfers onto imines originating from d-mannitol and (S)-(-)-2-methyl-2-propane sulfinamide or ascorbic acid and (R)-(-)-2-methyl-2-propane sulfinamide.

S-Methylidene Agents: Preparation of Chiral Non-Racemic Heterocycles.

Reaction of sulfur ylide with aldehyde, imine, and ketone functionality affords the desired three-membered heterocycle in excellent yield. The sulfur ylide is generated in situ upon decarboxylation of carboxymethylsulfonium betaine functionality. Of the seven carboxymethylsulfonium betaine derivatives surveyed, the highest level of conversion of π-acceptor to heterocycle was obtained having S-methyl and S-phenyl functionality bound to a thioacetate derivative. Methylene aziridinations and epoxidations involving the decarboxylation of carboxymethylsulfonium betaine functionality complements existing technologies with the advantages of the reaction protocol, levels of conversion and scope. While moderate levels of diastereocontrol were observed in the aziridination of imine functionality, the four oxiranes resolved using Jacobsen's Co(II)-salen complex were obtained in both high yield and enantioselectivity. The isolated chiral non-racemic oxiranes constitute the formal synthesis of chelonin-B and combretastatin starting from 3-bromo-4-methoxybenzaldehyde and 3,4,5-trimethoxybenzaldehyde respectively.

Synthesis of Chiral Aziridines through Decarboxylative Generation of Sulfur Ylides and their Reaction with Chiral Sulfinyl Imines.

Reaction of sulfur ylide with a series of aryl substituted chiral non-racemic sulfinyl imines afforded the corresponding aziridines in high yield and good stereoselection. The sulfur ylides were generated by the thermally induced decarboxylation of carboxymethylsulfonium betaines. A drop in the diastereomeric ratio was observed when going from electron deficient to electron releasing aryl substituted imines. Sulfonium methylidene aziridinations involving the decarboxylation of carboxymethylsulfonium betaine functionality compliments existing technologies with the advantages of the reaction protocol, levels of conversion and scope.

Asymmetric aerobic oxidation of alpha-hydroxy acid derivatives by C4-symmetric, vanadate-centered, tetrakisvanadyl(V) clusters derived from N-salicylidene-alpha-aminocarboxylates.

A series of chiral vanadyl(V) methoxides bearing 3-t-butyl-5-substituted N-salicylene-L-valinate and L-t-leucinate as chiral auxiliaries has been prepared. In all cases except the 3,5-di-t-butyl analogue, they exist as monomers both in solution and in the single crystal state. In the case of the 3,5-di-t-butyl analogue, the architectural nature of the vanadyl(V) complex highly depends on the base used during the complex formation event. A pentanuclear C4-symmetric complex was formed when potassium salts were employed instead of the corresponding sodium salts. A central vanadate(V) unit serves to grip four identical chiral monomeric vanadyl(V) units together, by which a potassium ion sits on top of the four flanking units through carbonyl coordinations and serves to hold the whole cluster by cooperation with the central vanadate(V) unit. In comparison with the corresponding monomeric vanadyl(V) methoxide complex, the cluster complex was utilized to facilitate the asymmetric aerobic oxidations of various racemic alpha-hydroxyesters, -amides, and -thioesters with excellent selectivity factors (krel 40 to >500).

Highly enantioselective aerobic oxidation of alpha-hydroxyphosphonates catalyzed by chiral vanadyl(V) methoxides bearing N-salicylidene-alpha-aminocarboxylates.

An unprecedented vanadyl(V) methoxide complex 4 derived from 3,5-dibromo-N-salicylidene-l-tert-leucinate enables highly enantioselective aerobic oxidations of alpha-hydroxyphosphonates at ambient temperature with selectivity factors ranging from 3 to >99.

Unsymmetrical diaryl sulfones through palladium-catalyzed coupling of aryl boronic acids and arylsulfonyl chlorides.

[reaction: see text] A simple and efficient method for the synthesis of unsymmetrical diaryl sulfones using the palladium-catalyzed coupling of aryl boronic acids and arylsulfonyl chlorides has been developed. High product yields, a short reaction time, and mild reaction conditions are important features of this method.