First preparation and reaction of polymer-bound 1,2-diaza-1,3-butadienes. A convenient entry to 4-triphenylphosphoranylidene-4,5-dihydropyrazol-5-ones

Organocatalytic Asymmetric Michael Addition of Pyrazolin‐5‐ones to Nitroolefins with Bifunctional Thiourea: Stereocontrolled Construction of Contiguous Quaternary and Tertiary Stereocenters

“…Pyrazolin‐5‐ones, a class of important aza‐heterocycles, have exhibited a variety of applications as pharmaceutical agents,2a–e synthetic scaffolds in combinatorial and medicinal chemistry,2f,g photographic couplers,2h chelating agents in coordination chemistry,2i,j and agrochemical products 2k. In particular, 4‐substituted‐pyrazolin‐5‐ones frequently set up the core frame of numerous pharmaceutically compounds,3 such as edaravone, used in inhibiting protease‐resistant prion protein accumulation 2e,4.…”

Cultivating the Passion to Build Heterocycles from 1,2‐Diaza‐1,3‐dienes: the Force of Imagination

“…Polymer-bound DD can also be prepared by using both soluble poly(ethylene glycol) (PEG) [5] or insoluble polystyrene (PS) [6][7][8] supports. The coupling sites can be both the ester group in the 4-position [5][6][7] and the azo group [8] of the azo-ene systems (Figure 1).…”

“…The coupling sites can be both the ester group in the 4-position [5][6][7] and the azo group [8] of the azo-ene systems (Figure 1).…”

Effect of bond‐length alternation on the dipole hyperpolarizability of phenol blue

“…A pendant NH functionality of the linear product precursor consequently effects an intramolecular cleavage of the ester linkage to create the amide vestige (PACT N−C(O)). Numerous systems of this kind are to be found for every heterocycle listed in Table 10: diketopiperazines 26 ,50a–50i cyclic peptides 27 ,51a–51g lactams 28 ,52a–52c benzodiazepines 29 ,53 1,4‐benzodiazepine‐2,5‐diones 30 ,54a–54c hydantoins 31 ,55a–55m quinazoline‐2,4‐diones and pyrimidine‐2,4‐diones 32 ,56a–56d pyrazolones 33 ,57a–57d and 3 H ‐quinazoline‐4‐ones 34 58…”