Dihydropyridones: Catalytic Asymmetric Synthesis, N‐ to C‐Sulfonyl Transfer, and Derivatizations

Abstract

Scheme 1. Versatile route to N-and O-heterocyclic building blocks. Ts = p-toluenesulfonyl, LB = Lewis base.

The Construction of 3‐Methyl‐4‐arylpiperidines via a trans‐ Perhydroindolic Acid‐Catalyzed Asymmetric Aza‐Diels–Alder Reaction

“…[3] Considering its flexibility ande fficiency,t he asymmetric aza-Diels-Alder reaction is one of the most promising methodologies for the construction of piperidines with multiple stereocenters. [4][5][6][7][8][9] Several catalytic systems have been applied successfully to the above reaction. In 2006, Bode and co-workers reported ac hiral N-heterocyclic carbene (NHC)-catalyzeda za-Diels-Alder reactionb etween dienophiles and a,b-unsaturated imines, giving chiral dihydropyridinone productsi ng oody ields and with remarkable enantioselectivities.…”

“…[6] Ye andc o-workers developed an efficient asymmetric aza-Diels-Alder reaction by using an NHC catalyst derivedf rom l-pyroglutamic acid. [8] Chen and co-workers reported an asymmetric aza-Diels-Alder reaction of aldehydeso rk etones with 1-azadienes to provide piperidine derivatives with excellent asymmetric results. [8] Chen and co-workers reported an asymmetric aza-Diels-Alder reaction of aldehydeso rk etones with 1-azadienes to provide piperidine derivatives with excellent asymmetric results.…”

Enantioselective, NHC‐Catalyzed Annulations of Trisubstituted Enals and Cyclic N‐Sulfonylimines via α,β‐Unsaturated Acyl Azoliums

“…With respect to the enal partners, the reaction tolerated all tested E-enals including cinnamaldehyde, its derivatives (with electron-donating and electron-withdrawing groups), aliphatic and alkenyl side chains (18-20, Table 2). Saccharine-derived cyclic sulfonylimines bearing either aromatic or aliphatic substituents were competent reactions partners in good (23,24) to excellent (21,22) enantioselectivity. Sulfonylimine 15 (X = O, R 1 = H) was also found to be successful under these reaction conditions (25,26).…”

“…In the absence of oxidant, only homoenolate product 9 was detected (entry 5). Chiral N-mesityl substituted triazolium salt 1, [19] used together with Hünigs base, [2a, 20] proved to be an outstanding catalyst for the annulation, affording the desired dihydropyridinone [21] product exclusively in 99 % ee. The use of stronger bases such as DBU or other chiral azolium salts (i.e.…”

Dissociation of protonated N‐(3‐phenyl‐2H‐chromen‐2‐ylidene)‐ benzenesulfonamide in the gas phase: cyclization via sulfonyl cation transfer

“…Intramolecular sulfonyl migration has also been reported to occur effectively in the condensed phase, and it has received intense interest in organic synthesis, due to the high regioselectivity of the sulfonylation and the viewpoint of atom economy. [16][17][18][19] Interestingly, some of these processes involve the Nto C-sulfonyl transfer. [16,19] To the best our knowledge, however, no report has been found on the gas-phase Nto C-sulfonyl transfer, which deserves further investigation.…”