The use of (−)-8-phenylisoneomenthol and (−)-8-phenylmenthol in the enantioselective synthesis of 3-functionalized 2-azabicyclo[2.2.1]heptane derivatives via aza-Diels–Alder reaction

Catalytic, asymmetric azidations at carbonyls: achiral and meso-anhydride desymmetrisation affords enantioenriched γ-lactams

An unprecedented organocatalytic process involving the asymmetric addition of azide to meso-anhydrides has been developed, promoted by novel sulfamide-substituted Cinchona alkaloid-based catalysts. Readily available glutaric anhydrides can be smoothly converted to enantioenriched hemi-acyl azides and from there to either γ-amino acids or γ-lactams.

Mechanism, Stereoselectivity, and Role of O2 in Aza-Diels-Alder Reactions Catalyzed by Dinuclear Molybdenum Complexes: A Theoretical Study

The aza-Diels-Alder-type reaction between imines and functionalized alkenes is one of the most versatile approaches to obtain piperidine derivatives. When using the Lewis acid [Mo₂(OAc)₄] (CAT) as a catalyst, it was found that the activation of CAT by O₂ was essential for an efficient reaction. In this paper, the mechanism and stereoselectivity of the aza-Diels-Alder reaction between aromatic acyl hydrozones 1 and Danishefsky diene 2 under uncatalyzed and catalyzed (CAT not activated by O₂ and CAT activated by O₂) conditions have been studied by density functional theory (DFT) calculation. The results show that the uncatalyzed reaction is difficult to proceed at room temperature due to the high energy barrier. The CAT not activated by molecular oxygen has catalytic activity but not too much. When CAT is activated by O₂, CATO2 may be the correct catalytic species, which results in a dramatic increase of reaction activity. The reaction mechanisms with/without the catalyst are different. The uncatalyzed reaction is concerted for both the endo and exo pathways. For the CAT-catalyzed reaction, the endo pathway is concerted, but the exo pathway is nonconcerted and involves two steps. The endo product is the main product for the reaction catalyzed by CAT, while for reactions catalyzed by CATO1 and CATO2, the endo and exo products can be obtained. The reaction activity is directly correlated to the atomic charges of two coupling C atoms. Our work explains the experimental results, determines the structure of the O₂-activated catalyst species, and provides predictions for the reaction activity and stereoselectivity controlling.

Rational Design of Chiral Selenium-π-Acid Catalysts

A series of unprecedented chiral selenium-π-acid catalysts for the asymmetric, oxidative functionalization of alkenes has been developed. In total, eleven different chiral dihydrodiselenocine and (di-)alkoxyphenyl (di)selenide motifs have been synthesized in a concise, modal, and straightforward fashion. Commercially available, non-racemic alcohols have been predominantly used as chiral building blocks for the facile assembly of the selenium-π-acid catalysts. These species have been exemplarily applied to the enantioselective intermolecular imidation and intramolecular acyloxylation of two olefins using N-fluorobenzenesulfonimide (NFSI) and ambient air, respectively, as terminal oxidants. In part, the catalysts provide very good yields of up to 99% and enantiomeric ratios of up to 83.5:16.5 under aerobic conditions.

Mechanistic insights for the transprotection of tertiary amines with Boc2O via charged carbamates: access to both enantiomers of 2-azanorbornane-3-exo-carboxylic acids

Development of a synthetic methodology for the selective transprotection in hindered tertiary amines using Boc₂O under N–C hydrogenolysis catalyzed by Pd/C: access to both enantiomers of 2-azanorbornane-3-exo-carboxylates.

2-Azanorbornane--a versatile chiral aza-Diels-Alder cycloadduct: preparation, applications in stereoselective synthesis and biological activity

The review presents the achievements in the field of preparation of chiral 2-azanorbornyl derivatives and their application in various stereoselective reactions as well as in biomimetic studies.

trans-2-Tritylcyclohexanol as a chiral auxiliary in permanganate-mediated oxidative cyclization of 2-methylenehept-5-enoates: application to the synthesis of trans-(+)-linalool oxide

The permanganate-mediated oxidative cyclization of a series of 2-methylenehept-5-eneoates bearing different chiral auxiliaries was investigated, leading to the discovery of trans-2-tritylcyclohexanol (TTC) as a highly effective chiral controller for the formation of the 2,5-substituted THF diol product with high diastereoselectivity (dr ∼97:3). Chiral resolution of (±)-TTC, prepared in one step from cyclohexene oxide, afforded (-)-(1S,2R)-TTC (er >99:1), which was applied to the synthesis of (+)-trans-(2S,5S)-linalool oxide.

Methyl 2-diphenyl-phosphor-yloxy-2-aza-bicyclo-[2.2.1]hept-5-ene-3-exo-carboxyl-ate

In the title compound, C₂₀H₂₀NO₄P, the dihedral angle between the phenyl rings is 68.52 (7)°. In the crystal structure, the mol­ecules are linked by a weak C—H⋯π(arene) inter­action along [010] involving the phenyl CH group and the phenyl rings. There are no further significant inter­molecular inter­actions.