Synthesis of Enantiopure 2-Aryl(Alkyl)-2-trifluoromethyl-Substituted Morpholines and Oxazepanes

One-pot enantioselective construction of 3,4-dihydro-2H-1,4-oxazines over Ru/Au relay catalysis and its mechanistic serendipity

One-pot enantioselective construction of 3,4-dihydro-2H-1,4-oxazines have been developed through the transfer hydrogenation/cyclization enantio-relay process using Ru and Au bimetallic catalysts.

Synthesis of chiral 1,4-oxazepane-5-carboxylic acids from polymer-supported homoserine

The preparation of novel 1,4-oxazepane-5-carboxylic acids bearing two stereocenters is reported in this article. Fmoc-HSe(TBDMS)-OH immobilized on Wang resin was reacted with different nitrobenzenesulfonyl chlorides and alkylated with 2-bromoacetophenones to yield N-phenacyl nitrobenzenesulfonamides. Their cleavage from the polymer support using trifluoroacetic acid (TFA) led to the removal of the silyl protective group followed by spontaneous lactonization. In contrast, TFA/triethylsilane (Et₃SiH)-mediated cleavage yielded 1,4-oxazepane derivatives as a mixture of inseparable diastereomers. The regioselectivity/stereoselectivity depended on the substitution of the starting 2-bromoacetophenones and was studied in detail. Catalytic hydrogenation of the nitro group improved the separability of the resulting diastereomeric anilines, which allowed us to isolate and fully characterize the major isomers.

The preparation of novel 1,4-oxazepane-5-carboxylic acids bearing two stereocenters is reported in this article.

Diastereoselective Ritter-like Reaction on Cyclic Trifluoromethylated N,O-Acetals Derived from l-Tartaric Acid

Despite the presence of the highly electron-withdrawing fluorinated substituent, cyclic α-trifluoromethylated N-acyliminium ions were successfully generated from fluorinated O-acetyl-N,O-acetal l-tartaric acid derivatives. The addition of nitriles on these intermediates occurred with high to excellent syn diastereoselectivity and led, in most cases, to oxazolines and amides as single diastereomers. The diastereoselectivity of the addition and the nature of the reaction product depend on the substituents on the hydroxyl groups of the tartaric acid scaffold. This methodology gave access to enantiopure, highly functionalized 5-(trifluoromethyl)pyrrolidin-2-one derivatives, bearing the fluorinated substituent on a tetrasubstituted carbon.

7-endo selenocyclization reactions on chiral 3-prenyl and 3-cinnamyl-2-hydroxymethylperhydro-1,3-benzoxazine derivatives. A way to enantiopure 1,4-oxazepanes

Enantiopure 1,4-oxazepane derivatives have been prepared by selenocyclofunctionalization of chiral 3-prenyl- and 3-cinnamyl-2-hydroxymethyl-substituted perhydro-1,3-benzoxazine derivatives. The 7-endo-cyclization occurs in high yields and diastereoselection. The regio- and stereochemistry of the cyclization products was dependent on the substitution pattern of the double bond, the nature of the hydroxyl group and the experimental conditions.

Heterocycles via intramolecular platinum-catalyzed propargylic substitution

We report a Pt(II)-catalyzed cyclization of nucleophile-tethered propargylic acetates yielding substituted heterocycles containing multiple heteroatoms including morpholines, dioxanes and sulfamates with high cis-selectivity.

Synthesis of enantiopure 1,4-dioxanes, morpholines, and piperazines from the reaction of chiral 1,2-diols, amino alcohols, and diamines with vinyl selenones

The reactions of readily available vinyl selenones with enantiopure 1,2-diols, N-protected-1,2-aminoalcohols, and diamines gave substituted enantiopure 1,4-dioxanes, morpholines, and piperazines, respectively, in good to excellent yields. The same procedure was extended to the synthesis of thiomorpholine, benzodiazepine, and benzoxazepine. The reactions proceeded in one pot, in the presence of base, through a simple and novel application of the Michael-initiated, ring-closure (MIRC) reactions. The formed heterocycles constitute a framework that is observed in a large number of pharmaceutical compounds.