A laterally-fused N-heterocyclic carbene framework from polysubstituted aminoimidazo[5,1-b]oxazol-6-ium salts

• Andrew D. Gillie,
• Matthew G. Wakeling,
• Bethan L. Greene,
• Louise Male and
• Paul W. Davies

Beilstein J. Org. Chem. 2024, 20, 621–627, doi:10.3762/bjoc.20.54

• seen with imidazolidines (cf. for IPr TEP[Ir] = 2050.2 cm−1) [34]. A benchmarking exercise was then performed looking at the reactivity of 13 compared against reaction of symmetrical IPrAuCl across a range of known gold-mediated transformations of alkynes featuring intermolecular attack [35

Trifluoromethylated hydrazones and acylhydrazones as potent nitrogen-containing fluorinated building blocks

• Zhang Dongxu

Beilstein J. Org. Chem. 2023, 19, 1741–1754, doi:10.3762/bjoc.19.127

• . Keywords: acylhydrazones; difluoromethylation; dihydropyridazine; fluorinated building blocks; hydrazones; imidazolidines; pyrazoles; pyrazolidines; pyrazolines; trifluoromethylation; Introduction The introduction of fluorine into pharmaceuticals, agrochemicals, and materials can significantly enhance

• an extension of their trifluoromethyl acylhydrazone synthesis, Hu et al. reported that trifluoromethyl acylhydrazones react with azomethine ylides [118] and ethyl isocyanoacetate [119] to generate trifluoromethylated imidazolidines. They demonstrated then that trifluoromethyl acylhydrazones act as

Experimental and theoretical investigations into the stability of cyclic aminals

• Edgar Sawatzky,
• Antonios Drakopoulos,
• Martin Rölz,
• Christoph Sotriffer,
• Bernd Engels and
• Michael Decker

Beilstein J. Org. Chem. 2016, 12, 2280–2292, doi:10.3762/bjoc.12.221

• Tetraponera sp. [1][2]. It is also present in ligands of ruthenium-based catalysts for metathesis [3], in imidazolidines acting as antiprotozoal and antibacterial agents [4][5], in Tröger’s base derivatives with diverse applications [6][7][8][9][10][11][12][13][14] (e.g., asymmetric catalysis, supramolecular

Asymmetric synthesis of γ-chloro-α,β-diamino- and β,γ-aziridino-α-aminoacylpyrrolidines and -piperidines via stereoselective Mannich-type additions of N-(diphenylmethylene)glycinamides across α-chloro-N-sulfinylimines

• Gert Callebaut,
• Sven Mangelinckx,
• Pieter Van der Veken,
• Karl W. Törnroos,
• Koen Augustyns and
• Norbert De Kimpe

Beilstein J. Org. Chem. 2012, 8, 2124–2131, doi:10.3762/bjoc.8.239

• , comparable non-halogenated trans-imidazolidines were already synthesized by 1,3-dipolar cycloaddition of N-benzylidene glycine ester enolates across N-sulfinylaldimines in the presence of a Lewis acid [43]. The trans-stereochemistry of imidazolidine 12b was ensured by the vicinal coupling constant 3JH4-H5

• = 7.43 Hz and the 1H NMR chemical shift of H4 (3.85 ppm), which were in the same range as for closely related trans-imidazolidines and trans-oxazolidines [43][44][45]. The trans-imidazolidine 12b is a potential building block for foldamers, as the corresponding trans-oxazolidin-2-ones are already applied

• as such [46]. trans-Imidazolidine 12b could also be used as a precursor of the corresponding Nα,Nβ-deprotected α,β-diaminocarboxylamide, by hydrolysis under acidic conditions, in analogy with deprotection reactions of imidazolidines, imidazolines and oxazolines in the literature [16][47][48]. However

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• deoxy Breslow intermediates 45a–f can be described by Equation 1 [107]. In contrast to the situation described for the NHCs in Figure 23, the benzylidene-imidazolines 45a,d are now 103 times more nucleophilic than the corresponding benzylidene-imidazolidines 45c,f (Figure 24 and Figure 25a). The

• higher nucleophilicities of benzylidene-imidazolines compared with benzylidene-imidazolidines explain why imidazol-2-ylidenes but not imidazolidine-2-ylidenes are commonly used organocatalysts. Second-order rate constants for reactions of electrophiles with nucleophiles. Mechanism of amine-catalyzed

Chemistry of polyhalogenated nitrobutadienes, 10: Synthesis of highly functionalized heterocycles with a rigid 6-amino-3-azabicyclo[3.1.0]hexane moiety

• Viktor A. Zapol’skii,
• Jan C. Namyslo,
• Armin de Meijere and
• Dieter E. Kaufmann

Beilstein J. Org. Chem. 2012, 8, 621–628, doi:10.3762/bjoc.8.69

• recently published [19] analogues of imidacloprid (N-[1-[(6-chloro-3-pyridyl)methyl]-4,5-dihydroimidazol-2-yl]nitramide), the substitutions of the imidazolidines 9 and 10 with 1 were also tested. Compounds 9 and 10 were prepared from the nitrodiene 3 and the ethylenediamines 7 and 8. The formal

Asymmetric synthesis of biaryl atropisomers by dynamic resolution on condensation of biaryl aldehydes with (−)-ephedrine or a proline- derived diamine

• Ann Bracegirdle,
• Jonathan Clayden and
• Lai Wah Lai

Beilstein J. Org. Chem. 2008, 4, No. 47, doi:10.3762/bjoc.4.47

• imidazolidines [25][27], ephedrine-derived oxazolidines [26][27], and, most extensively, sulfoxides [16][29][30][31]. These perform well when a powerful electronic or steric bias is evident about the atropisomeric bond over which control is applied [32], and in the case of atropisomeric amides have offered

• substrates Previous success with stereocontrol employing ephedrine-derived oxazolidines [15][26][27][34][35] and proline-derived imidazolidines [25][27] prompted us to investigate the thermal stability and conformational preferences of similar products arising from condensation reactions of 2-formylbiaryls

• stereogenic centre, in accordance with literature precedent [15][25][26][27][34][35]. At temperatures below 70 °C, mixtures of diastereoisomeric imidazolidines 9 and oxazolidines 10 were observed with rather poor and somewhat variable selectivity (1:1–1.5:1). However, as the temperature rose above 80 °C in