A novel synthesis of enantiopure octahydropyrrolo[3,4-b]pyrroles by intramolecular [3 + 2] dipolar cycloaddition on chiral perhydro-1,3-benzoxazines

A New Synthetic Route to Polyhydrogenated Pyrrolo[3,4-b]pyrroles by the Domino Reaction of 3-Bromopyrrole-2,5-Diones with Aminocrotonic Acid Esters

A new synthetic approach to polyfunctional hexahydropyrrolo[3,4-b]pyrroles was developed based on cyclization of N-arylbromomaleimides with aminocrotonic acid esters. A highly chemo- and stereoselective reaction is a Hantzsch-type domino process, involving the steps of initial nucleophilic C-addition or substitution and subsequent intramolecular nucleophilic addition without recyclyzation of imide cycle.

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.

Diastereoselective synthesis of enantiopure morpholines by electrophilic selenium-induced 6-exo cyclizations on chiral 3-allyl-2-hydroxymethylperhydro-1,3-benzoxazine derivatives

Enantiopure morpholine derivatives have been prepared by selenocyclofunctionalization of chiral 3-allyl-2-hydroxymethyl-substituted perhydro-1,3-benzoxazine derivatives. The cyclization occurs in high yields and diastereoselection, although the temperature of the reaction and the structure of the substituent at C-2 and the substitution pattern of the double bond can modify the regio- and stereochemistry of the final products.

Diastereoselective Yang Photocyclization Reactions in Solution. Synthesis of Enantiopure Azetidin-3-ol Derivatives

[reaction: see text] Chiral 2-acyl-3-allyl- or 2-acyl-3-benzyl-substituted perhydro-1,3-benzoxazines readily cyclized under irradiation to azetidin-3-ol derivatives. The diastereoselectivity of the cyclization is dependent on the nature of the substituents at the nitrogen atom. N-allyl-substituted derivatives yielded only two of the four possible diastereomers in moderate to good diastereomeric excess. The cyclization of N-benzyl derivatives was totally diastereoselective leading to a single diastereomer. The elimination of the menthol appendage lead to enantiopure 2,3-disubstituted azetidin-3-ol derivatives.

Synthesis of enantiopure 3-azabicyclo[3.2.0]heptanes by diastereoselective intramolecular [2+2] photocycloaddition reactions on chiral perhydro-1,3-benzoxazines

[2+2] photocycloadditions involving chiral 3-acryloyl-2-vinylperhydro-1,3-benzoxazines derived from (-)-8-aminomenthol are highly diastereoselective reactions. The facial selectivity depends on the type of substitution at the vinyl double bond, and always leads to cis-fused bicyclic derivatives. The de is good for compounds with one substituent at the outer carbon of the double bond at C-2, but only one diastereomer is formed in cyclizations of compounds with two substituents at that position. The elimination of the menthol appendage gives enantiopure 3-azabicyclo[3.2.0]heptanes.

Temperature- and time-dependent stereochemical control in thermally induced keto-ene cyclizations

Reaction conditions determine the stereoselection in the intramolecular keto-ene reaction. The thermolysis of chiral 2-acyl-3-allyl-substituted 1,3-perhydrobenzoxazines derived from (-)-8-aminomenthol gives a mixture of only two cis-3-hydroxy-3,4-disubstituted pyrrolidine nuclei. The stereochemistry of the major diastereoisomer depends on both the temperature and the reaction time.