Chlorosulfonamide Salts Are Superior Electrophilic Chlorine Precursors for the Organocatalytic Asymmetric Chlorocyclization of Unsaturated Amides

Chloramine-T·3H₂O and other chlorosulfonamide salts can serve as readily available, stable, and inexpensive precursors of electrophilic chlorine in the organocatalytic asymmetric chlorofunctionalization of olefins. In conjunction with commercially available organocatalysts, they can be utilized in the asymmetric chlorocyclization of unsaturated amides to yield products with unprecedented levels of stereoselectivity even at ambient temperatures and high concentrations

Kinetic Resolution of Unsaturated Amides in a Chlorocyclization Reaction: Concomitant Enantiomer Differentiation and Face Selective Alkene Chlorination by a Single Catalyst

The first example of a kinetic resolution via chlorofunctionalization of olefins is reported. The enantiomers of racemic unsaturated amides were found to have different hydrogen-bonding affinities for chiral Lewis bases in numerous solvents. This interaction was exploited in developing a kinetic resolution of racemic unsaturated amides via halocyclization. The same catalyst serves to both “sense chirality” in the substrate as well as mediate a highly face-selective chlorine delivery onto the olefin functionality, resulting in stereotriad products in up to 99:1 <i>dr</i> and up to 98.5:1.5 <i>er</i>. The selectivity factors were typically greater than 50 to allow for the simultaneous synthesis of both the products and unreacted substrates in highly enantioenriched form at yields approaching 50%. The reaction employs catalytic amounts (≤0.50 mol %) of a commercially available and recyclable organocatalyst

Kinetic Resolution of Unsaturated Amides in a Chlorocyclization Reaction: Concomitant Enantiomer Differentiation and Face Selective Alkene Chlorination by a Single Catalyst

The first example of a kinetic resolution via chlorofunctionalization of olefins is reported. The enantiomers of racemic unsaturated amides were found to have different hydrogen-bonding affinities for chiral Lewis bases in numerous solvents. This interaction was exploited in developing a kinetic resolution of racemic unsaturated amides via halocyclization. The same catalyst serves to both “sense chirality” in the substrate as well as mediate a highly face-selective chlorine delivery onto the olefin functionality, resulting in stereotriad products in up to 99:1 <i>dr</i> and up to 98.5:1.5 <i>er</i>. The selectivity factors were typically greater than 50 to allow for the simultaneous synthesis of both the products and unreacted substrates in highly enantioenriched form at yields approaching 50%. The reaction employs catalytic amounts (≤0.50 mol %) of a commercially available and recyclable organocatalyst

Kinetic Resolution of Unsaturated Amides in a Chlorocyclization Reaction: Concomitant Enantiomer Differentiation and Face Selective Alkene Chlorination by a Single Catalyst

The first example of a kinetic resolution via chlorofunctionalization of olefins is reported. The enantiomers of racemic unsaturated amides were found to have different hydrogen-bonding affinities for chiral Lewis bases in numerous solvents. This interaction was exploited in developing a kinetic resolution of racemic unsaturated amides via halocyclization. The same catalyst serves to both “sense chirality” in the substrate as well as mediate a highly face-selective chlorine delivery onto the olefin functionality, resulting in stereotriad products in up to 99:1 <i>dr</i> and up to 98.5:1.5 <i>er</i>. The selectivity factors were typically greater than 50 to allow for the simultaneous synthesis of both the products and unreacted substrates in highly enantioenriched form at yields approaching 50%. The reaction employs catalytic amounts (≤0.50 mol %) of a commercially available and recyclable organocatalyst

Absolute Stereochemical Determination of Asymmetric Sulfoxides via Central to Axial Induction of Chirality

The absolute configuration of chiral sulfoxides is determined by means of host–guest complexation that leads to the induction of axial chirality in an achiral host. The central to axial induction of helicity is rationalized by a simple recognition of the relative length and size of the substituents attached to the S-center. This technique is used to determine the absolute configuration of chiral sulfoxides, requiring micrograms of sample, without the need for prefunctionalization

Absolute Stereochemical Determination of Asymmetric Sulfoxides via Central to Axial Induction of Chirality

The absolute configuration of chiral sulfoxides is determined by means of host–guest complexation that leads to the induction of axial chirality in an achiral host. The central to axial induction of helicity is rationalized by a simple recognition of the relative length and size of the substituents attached to the S-center. This technique is used to determine the absolute configuration of chiral sulfoxides, requiring micrograms of sample, without the need for prefunctionalization

Absolute Configuration for 1,<i>n</i>-Glycols: A Nonempirical Approach to Long-Range Stereochemical Determination

The absolute configurations of 1,<i>n</i>-glycols (<i>n</i> = 2–12, 16) bearing two chiral centers were rapidly determined via exciton-coupled circular dichroism (ECCD) using a tris­(pentafluorophenyl)­porphyrin (TPFP porphyrin) tweezer system in a nonempirical fashion devoid of chemical derivatization. A unique “side-on” approach of the porphyrin tweezer relative to the diol guest molecule is suggested as the mode of complexation

Absolute Configuration for 1,<i>n</i>-Glycols: A Nonempirical Approach to Long-Range Stereochemical Determination

The absolute configurations of 1,<i>n</i>-glycols (<i>n</i> = 2–12, 16) bearing two chiral centers were rapidly determined via exciton-coupled circular dichroism (ECCD) using a tris­(pentafluorophenyl)­porphyrin (TPFP porphyrin) tweezer system in a nonempirical fashion devoid of chemical derivatization. A unique “side-on” approach of the porphyrin tweezer relative to the diol guest molecule is suggested as the mode of complexation

Absolute Configuration for 1,<i>n</i>-Glycols: A Nonempirical Approach to Long-Range Stereochemical Determination

The absolute configurations of 1,<i>n</i>-glycols (<i>n</i> = 2–12, 16) bearing two chiral centers were rapidly determined via exciton-coupled circular dichroism (ECCD) using a tris­(pentafluorophenyl)­porphyrin (TPFP porphyrin) tweezer system in a nonempirical fashion devoid of chemical derivatization. A unique “side-on” approach of the porphyrin tweezer relative to the diol guest molecule is suggested as the mode of complexation

Point-to-Axial Chirality TransferA New Probe for “Sensing” the Absolute Configurations of Monoamines

A host molecule, capable of freely adopting <i>P</i> or <i>M</i> helicity, is described for molecular recognition and chirality sensing. The host, consisting of a biphenol core, binds chiral amines via hydrogen-bonding interactions. The diastereomeric complex will favor either <i>P</i> or <i>M</i> helicity as a result of minimizing steric interactions of the guest molecule with the binding cavity of the host, resulting in a detectable exciton-coupled circular dichroic spectrum. A working model is proposed that enables non-empirical prediction of the chirality of the bound amine