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Overcrowded alkenes are expeditiously prepared by the versatile Barton–Kellogg olefination and have remarkable applications as functional molecules owing to their unique stereochemical features. The induced stereodynamics thereby enable the controlled motion of molecular switches and motors, while the high configurational stability prevents undesired isomeric scrambling. Bistricyclic aromatic enes are prototypical overcrowded alkenes with outstanding stereochemical properties, but their stereocontrolled preparation was thus far only feasible in stereospecific reactions and with chiral auxiliaries. Herein we report that direct catalyst control is achieved by a stereoselective Barton–Kellogg olefination with enantio‐ and diastereocontrol for various bistricyclic aromatic enes. Using Rh2(S‐PTAD)4 as catalyst, several diazo compounds were selectively coupled with a thioketone to give one of the four anti‐folded overcrowded alkene stereoisomers upon reduction. Complete stereodivergence was reached by catalyst control in combination with distinct thiirane reductions to provide all four stereoisomers with e.r. values of up to 99:1. We envision that this strategy will enable the synthesis of topologically unique overcrowded alkenes for functional materials, catalysis, energy‐ and electron transfer, and bioactive compounds. [ABSTRACT FROM AUTHOR]

The reductive amination of (−)-2-carene-3-aldehyde, prepared in two steps from (−)-perillaldehyde, furnished 2-carene-based allylamines. tert-Butyloxycarbonyl (Boc) or carbobenzyloxy (Cbz) protection of the resulting amines, followed by stereoselective dihydroxylation in highly stereospecific reactions with OsO4 and subsequent deprotection, resulted in N-benzylaminodiols, which were transformed to primary and tertiary aminodiols. The reactions of the N-benzyl- and N-(1-phenylethyl)-substituted derivatives with formaldehyde led to highly regioselective ring closure, resulting in carane-fused 1,3-oxazines. The aminodiols and their 1,3-oxazine derivatives were applied as chiral catalysts in the enantioselective addition of diethylzinc to aldehydes. The best ( R) enantioselectivity was observed in the case of the N-(( R)-1-phenylethyl)-substituted aminodiol, whereas the opposite chiral direction was preferred when the 1,3-oxazines were applied. Through the use of molecular modelling at an ab initio level, this phenomenon was interpreted in terms of competing reaction pathways. Molecular modelling at the RHF/LANL2DZ level of theory was successfully applied for a mechanism-based interpretation of the stereochemical outcome of the reactions leading to the development of further 1,3-oxazine-based ligands, which display excellent ( S) enantioselectivity (95 and 98 % ee) in the examined transformation. [ABSTRACT FROM AUTHOR]

A process for the production of poly(lactic acid) with a melting point of > 150 °C from racemic lactide was developed. Only process steps that are usable in an industrial process were included to ensure an easy transfer to a commercial scale. A stereoselective catalyst system for lactide melt phase polymerization comprising of an Al-salen initiator, a hydroxyl cocatalyst and an acidic quenching additive was developed. Monomer recovery aspects, temperature variation and different catalyst concentrations were evaluated to allow for a high yield process which can be transferred to a technical scale. [ABSTRACT FROM AUTHOR]

A bimetallic heme-DNA cofactor, containing an iron and a copper center, was synthesized for the design of novel hybrid catalysts for stereoselective synthesis. The cofactor was used for the reconstitution of apo-myoglobin. Both the cofactor alone and its myoglobin adduct were used to catalyze a model Diels Alder reaction. Stereoselectivity of this conversion was analyzed by chiral HPLC. Reactions carried out in the presence of myoglobin-heme-Cu-DNA catalyst showed greater product conversion and stereoselectivity than those carried out with the heme-Cu-DNA cofactor. This observation suggested that the protein shell plays a significant role in the catalytic conversion. [ABSTRACT FROM AUTHOR]

Highly efficient stereoselective 1.4-addition of racemic α-fluoro-αnitro(phenylsulfonyl)methane (FNSM) as a fluoromethyl pronucleophile to α,β-unsaturated ketones using a wide range of chiral organobifunctional catalysts under moderate conditions in the absence of an additional base has been achieved. A series of catalysts was screened for the enantioselective addition of FNSM to chalcones and the catalysts CN I. CD I, QN l-IV, and QD I were found to enable this reaction, successfully providing exclusive 1,4-addition products stereoselectively in high yields (conversion, diastereomeric ratio, and enantiomeric excess). Studies involving a model reaction and systematic analysis of the absolute configuration support the suggested mechanism. [ABSTRACT FROM AUTHOR]