Syndiotactic PLA from meso-LA polymerization at Al-chiral complex: a probe of DFT mechanistic insights

The mechanism(s) for the formation of syndiotactic PLA by ROP of meso-LA by chiral-Al-complex are disclosed by DFT calculations. The contributions toward stereoselectivity has been analized confirming the peculiar chiral...

A hidden catalysis: metal-, and organocatalyst-free one-pot assembly of chiral aza-tricyclic molecules containing six contiguous stereocenters

<p></p><p>Chiral molecules with their defined 3-D structures are of paramount importance for the study of chemical biology and drug discovery. Having rich structural diversity and unique stereoisomerism, chiral molecules offer a large chemical space that can be explored for the design of new therapeutic agents.¹ In practice, chiral architectures are usually prepared from organometallic and organocatalytic processes where a transition metal or an organocatalyst is tailor-made for a desired reaction. As a result, developing a method that enables rapid assembly of chiral complex molecules under a metal- and organocatalyst-free condition represents a daunting challenge. Here we developed a straightforward one-pot procedure to create a chiral 3-D structure from 2-D structures and an amino acid without any chiral catalyst. The center of this research is the design of a <a>special chiral spiroimidazolidinone cyclohexadienone intermediate</a>, a merger of a chiral reactive substrate with multiple nucleophillic/electrophillic sites and a transient organocatalyst. <a>This unique substrate-catalyst (“sub-catalyst”) dual role of the intermediate was displayed in its aza-Michael/Michael cascade reaction with an </a>α,β-unsaturated aldehyde under an iminium/enamine catalysis. <a>The enhanced co-ordinational proximity of the chiral substrate and catalyst</a> in the transition state resulted in a substantial steric discrimination and an excellent overall diastereoselectivity. Aza-tricylic molecules with six contiguous stereocenters were assembled from <i>N</i>-alkylated aminophenols, α,β-unsaturated aldehydes and chiral α-amino acids under a hidden “sub-catalysis” where the strategically produced “sub-catalyst” does not present in initial components of the reaction. The success of this methodology will pave the way for many efficient preparations of chiral complex molecules.</p><br><p></p>

A hidden catalysis: metal-, and organocatalyst-free one-pot assembly of chiral aza-tricyclic molecules containing six contiguous stereocenters

<p></p><p>Chiral molecules with their defined 3-D structures are of paramount importance for the study of chemical biology and drug discovery. Having rich structural diversity and unique stereoisomerism, chiral molecules offer a large chemical space that can be explored for the design of new therapeutic agents.¹ In practice, chiral architectures are usually prepared from organometallic and organocatalytic processes where a transition metal or an organocatalyst is tailor-made for a desired reaction. As a result, developing a method that enables rapid assembly of chiral complex molecules under a metal- and organocatalyst-free condition represents a daunting challenge. Here we developed a straightforward one-pot procedure to create a chiral 3-D structure from 2-D structures and an amino acid without any chiral catalyst. The center of this research is the design of a <a>special chiral spiroimidazolidinone cyclohexadienone intermediate</a>, a merger of a chiral reactive substrate with multiple nucleophillic/electrophillic sites and a transient organocatalyst. <a>This unique substrate-catalyst (“sub-catalyst”) dual role of the intermediate was displayed in its aza-Michael/Michael cascade reaction with an </a>α,β-unsaturated aldehyde under an iminium/enamine catalysis. <a>The enhanced co-ordinational proximity of the chiral substrate and catalyst</a> in the transition state resulted in a substantial steric discrimination and an excellent overall diastereoselectivity. Aza-tricylic molecules with six contiguous stereocenters were assembled from <i>N</i>-alkylated aminophenols, α,β-unsaturated aldehydes and chiral α-amino acids under a hidden “sub-catalysis” where the strategically produced “sub-catalyst” does not present in initial components of the reaction. The success of this methodology will pave the way for many efficient preparations of chiral complex molecules.</p><br><p></p>

Metal-, and Organocatalyst-Free One-Pot Assembly of Chiral Aza-Tricyclic Molecules: Creating Six Contiguous Stereocenters from 2-D-Structures and an Amino Acid

<p>Chiral molecules with their defined 3-D structures are of paramount importance for the study of chemical biology and drug discovery. Having rich structural diversity and unique stereoisomerism, chiral molecules offer a large chemical space that can be explored for the design of new therapeutic agents.¹ Practically, chiral architectures are usually prepared from organometallic and organocatalytic processes where a transition metal or an organocatalyst is tailor-made for desired reactions. As a result, developing a method that enables rapid assembly of chiral complex molecules under metal- and organocatalyst-free condition represents a daunting challenge. Here we developed a straightforward route to create a chiral 3-D structure from 2-D structures and an amino acid without any chiral catalyst. The center of this research is the design of a <a>special chiral spiroimidazolidinone cyclohexadienone intermediate</a>, a merger of a chiral reactive substrate with multiple nucleophillic/electrophillic sites and a transient organocatalyst. <a>This unique substrate-catalyst (“subcatalyst”) dual role of the intermediate enhances </a><a>the coordinational proximity of the chiral substrate and catalyst</a> in the key Aza-Michael/Michael cascade resulting in a substantial steric discrimination and an excellent overall diastereoselectivity. Whereas the “subcatalyst” (hidden catalyst) is not present in the reaction’s initial components, which renders a chiral catalyst-free process, it is strategically produced to promote sequential self-catalyzed reactions. The success of this methodology will pave the way for many efficient preparations of chiral complex molecules and aid for the quest to create next generation of therapeutic agents.</p>

Controlling orthogonal self-assembly through cis–trans isomerization of a non-covalent palladium complex dimer

Self-assembly of a chiral complex dimer held by 16 hydrogen bonds was controlled through configurational isomerization of the metal center.

A highly enantioselective Hg(ii)-catalyzed Sakurai–Hosomi reaction of isatins with allyltrimethylsilanes

A chiral complex derived from (S)-difluorophos and Hg(OTf)2 is identified as a powerful catalyst for the Sakurai–Hosomi reaction of isatins with allyltrimethylsilane, allowing the facile synthesis of valuable building blocks 3-allyl-3-hydroxyoxindoles in up to 97% ee, with only 0.5–1.0 mol% of catalyst loading.