Preparation of Carbodiimides with One-Handed Axial Chirality

Abstract

The axial chirality of carbodiimide was proposed in 1932, but the synthesis of carbodiimide with one-handed axial chirality has not been achieved because of the low barrier of racemization. This work presents a strategy to use a conformationally restrained cyclic structure for creating carbodiimides whose biases of the axial chirality (labeled as S NCN /R NCN ) are higher than 100:1, as determined by vibrational circular dichroism spectroscopy and density functional theory calculations.

Nucleophilic Cyclization/Electrophilic Substitution of (2,2-Dialkoxyethyl)ureas: Highly Regioselective Access to Novel 4-(Het)arylimidazolidinones and Benzo[d][1,3]diazepinones

“…27 The conventional approach to cyclic ureas involves carbonylation of variously substituted diamines with phosgene. 28,29 Much effort has been made to replace phosgene by its less toxic analogues, such as dialkyl carbonates, 30,31 triphosgene, [32][33][34] 1,1′-carbonyldiimidazole, 35,36 urea, 37 and others. Novel approaches to these compounds, such as the direct carbonylation with carbon monoxide 38,39 or [3+2] cycloaddition of isocyanoacetates with nitrones, 40 are still emerging, indicating a growing area of interest.…”

Enantiodivergent One‐Pot Synthesis of Axially Chiral Biaryls Using Organocatalyst‐Mediated Enantioselective Domino Reaction and Central‐to‐Axial Chirality Conversion

“…Not only substituted phenyl groups but also substrates possessing 1-naphthyl and 1-(4-methoxy) naphthyl groups gave high (S a )-selectivity (entries 9 and 10). The 1-nitronaphthalene moiety of biaryls was also investigated and it was found that when the 6-or 7-position of 1nitronaphthalene was substituted with a bromine atom, good (S a )-selectivity was observed (entries [11][12][13][14]. In most cases one-…”

“…The S a absolute configuration of the biaryl 5 a obtained using Method A was determined based on its vibrational circular dichroism (VCD) spectrum; [13] the calculated spectrum of the (S a )-isomer matches well with the observed spectrum, as shown in Figure 1.…”

Inversion of the Axial Information during Oxidative Aromatization in the Synthesis of Axially Chiral Biaryls with Organocatalysis as a Key Step

“…We determinedt he absolutec onfiguration of 3a by X-ray crystallographic analysis (Figure 3), and those of 3e and 3f on the basis of CD and VCD [19] in combination with DFT calculations. In all cases of 3a-3f,t he axial information was completely inverted and R a enantiomerswere obtained.…”