In the present study, mechanistic insights into the domino reaction between 1,4-dithiane-2,5-diol and azomethine imines were derived from the computational study with B3LYP and M06-2X functionals. On the whole, the domino process comprises two consecutive reactions: cleavage of 1,4-dithiane-2,5-diol leading to mercaptoacetaldehyde and [3 + 3] cycloaddition of mercaptoacetaldehyde with azomethine imines. The cleavage of 1,4-dithiane-2,5-diol can take place via multiple possible pathways (1A-1E), and pathway 1E in which double-methanol molecules mediate the proton transfer process is the most energetically favorable, with an energy barrier of 19.9 kcal mol(-1). For the [3 + 3] cycloaddition, three possible pathways (2F-2H) were explored. The calculated energy profiles reveal that pathway 2H with activation energies ranging from 6.9 to 10.2 kcal mol(-1) is more energetically favorable than pathways 2F and 2G. Specifically, pathway 2H comprises three reaction steps: deprotonation of mercaptoacetaldehyde by DABCO allows for the formation of the thiol anion, which subsequently launches a nucleophilic attack on azomethine imines followed by intramolecular cyclization resulting in the final products. The calculated results are in agreement with the experimental observations that the reaction can proceed most efficiently in the presence of both DABCO and methanol. Furthermore, the hydrogen bonding interaction is identified to be the main factor determining the observed diastereoselectivity The current systematic theoretical study gives a full scenario of the reaction between 1,4-dithiane-2,5-diol and azomethine imines catalyzed by DABCO, and thus provides some valuable clues for further investigation and development of this kind of important reaction.

The enantioselective synthesis of fluorinated tricyclic chromanones with multiple vicinal stereogenic centers has been realized for the first time, through the tandem reaction between 2-fluorinated 1-(2-hydroxyaryl)-1,3-diketones and α,β-unsaturated aldehydes. In...

Amino‐acid‐derived phosphine catalyzed [4+2] cycloaddition leading to chiral tetrahydropyridines, making use of α‐substituted allenic ketones as “C4 synthons” and N‐sulfonyl cyclic ketimines, has been developed. This asymmetric cycloaddition tolerates a wide range of α‐substituted allenic ketones. A series of chiral sultam‐fused tetrahydropyridines bearing a quaternary stereocenter were obtained in high yields with good enantioselectivities.

An enantioselective approach to lactonefused chromanone derivatives from 1-(2-hydroxyaryl)-1,3-diketones and α,β-unsaturated aldehydes under mild conditions has been developed, which included organocatalytic stepwise Michael addition/ cycloketalization/hemiacetalization and followed by oxidation reaction. In the presence of chiral amine organocatalyst and an additional salicylic acid, a wide range of 1-(2-hydroxyaryl)-1,3-diketones and α,β-unsaturated aldehydes were tolerated, furnishing a spectrum of lactone-fused tricyclic chromanones bearing three contiguous stereocenters in high yields with good to excellent selectivities (90-> 99% ee, > 19:1 d.r.).

The palladium-catalyzed chemo-and stereoselective [2 + 2 + 2] annulation reaction of 2-(2-enynyl)pyridines with arynes has been developed. A wide range of (E)-or (E/Z)-isomers of 2-(2-enynyl)pyridines and arynes was tolerated, providing a spectrum of (E)-phenanthrenylated 2-alkenylpyridines in good yield, together with the generation of a chiral axis between an alkene and a phenanthrene ring. Note pubs.acs.org/joc