Systematic Evaluation of Sulfoxides as Catalysts in Nucleophilic Substitutions of Alcohols

Expanding the Use of Peroxygenase from Oat Flour in Organic Synthesis: Enantioselective Oxidation of Sulfides

Biocatalyzed oxidations are an important target in sustainable synthesis since chemical oxidations often require harsh conditions and metal-based catalysts. A raw peroxygenase-containing enzymatic preparation from oat flour was tested as a biocatalyst for the enantioselective oxidation of sulfides to sulfoxides and the variations of some reaction parameters were evaluated. Under optimal conditions, thioanisole was fully converted into the corresponding (R)-sulfoxide with high optical purity (80% ee) and the same stereopreference was maintained in the oxidation of some other sulfides. Changes in the substituent on the sulfur atom affected the selectivity of the enzyme and the best results were obtained with phenyl methoxymethyl sulfide, which gave the corresponding sulfoxide in 92% ee as exclusive product. The over-oxidation of sulfides to sulfones was instead detected in all the other cases and preferential oxidation of the (S)-enantiomer of the sulfoxide intermediate was observed, albeit with low selectivity. Carrying out the oxidation of thioanisole up to the 29% formation of sulfone led to enhancement of the sulfoxide optical purity (89% ee). The activity in sulfoxidation reactions, in addition to that reported in the epoxidation of different substrates, makes this plant peroxygenase a promising and useful tool in organic synthesis.

2,4,6-Trimethylbenzyl Chloride (α2-Chloroisodurene)

The X-ray structure of the title compound has been determined and it is compared with those of other substituted benzyl chlorides reported previously. It has an atypically long CH2–Cl bond.

Cyano-borrowing: titanium-catalyzed direct amination of cyanohydrins with amines and enantioselective examples

The direct amination of cyanohydrins with amines via a catalytic cyano-borrowing reaction was developed. The transformation features broad substrate scope, excellent functional group compatibility, and very mild and simple operations. Moreover, a titanium catalyst supported by quinine and (S)-BINOL ligands enabled an asymmetric cyano-borrowing reaction with moderate to high enantioselectivity.

Promotion of Appel-type reactions by N-heterocyclic carbenes

N-Heterocyclic carbenes are found to mediate the Appel-type dehydrative halogenation reaction.