Nitroso and Azo Compounds in Modern Organic Synthesis: Late Blooming but Very Rich

Yamamoto, Hisashi; Kawasaki, Masanori

doi:10.1246/bcsj.80.595

Cited by 161 publications

(57 citation statements)

References 100 publications

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“…[41] The observed stereochemistry can be rationalized by an analogous transition-state model in which nitrosobenzene approaches the Si face of the s-cis-enamine, as directed by the triflamide group (Figure 1c). Because activation of nitrosobenzene by strong acids such as carboxylic acid and tetrazole is necessary to obtain the aminoxylation product, [42] only a combination of the s-cis-enamine and nitrosobenzene activated on the Si face of the enamine can provide the S isomer. This observation strongly suggests the existence of the s-cis-enamine intermediate in the Mannich and aldol reactions catalyzed by (S)-3 reported herein.…”

Section: A C H T U N G T R E N N U N G [Mol %]mentioning

confidence: 99%

A Designer Axially Chiral Amino Sulfonamide as an Efficient Organocatalyst for Direct Asymmetric anti‐Selective Mannich Reactions and syn‐Selective Cross‐Aldol Reactions

Kano

Yamaguchi

Maruoka

2009

Chemistry A European J

117

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A direct asymmetric Mannich reaction using a novel axially chiral amino sulfonamide (S)-3 that is highly anti- and enantioselective has been developed. For instance, in the presence of a catalytic amount of (S)-3, the reactions between aldehydes and alpha-imino esters proceeded smoothly to give anti Mannich products with a significantly higher anti/syn ratio and enantioselectivity than previously possible. By utilizing N-Boc-protected aromatic imines instead of alpha-imino esters, the synthetically useful Boc protecting group and various aromatic or heteroaromatic substituents were installed into the anti Mannich products and consequently the substrate scope of the anti-selective Mannich reaction and the synthetic utility of the anti Mannich products have been expanded. The axially chiral amino sulfonamide (S)-3 has also been successfully applied to asymmetric direct cross-aldol reaction between two different aldehydes. The catalyst (S)-3 has the advantage of giving mainly syn products, whereas proline shows the opposite anti selectivity.

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Section: A C H T U N G T R E N N U N G [Mol %]mentioning

confidence: 99%

A Designer Axially Chiral Amino Sulfonamide as an Efficient Organocatalyst for Direct Asymmetric anti‐Selective Mannich Reactions and syn‐Selective Cross‐Aldol Reactions

Kano

Yamaguchi

Maruoka

2009

Chemistry A European J

117

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“…[188] Either, the reduction from the nitro group to the nitroso (which is in fact an insitu reduction of the nitro group to the amine followed by an oxidation to the nitroso), [209] or a stepwise procedure including the reduction to the amine and subsequent oxidation to the nitroso. [189] [210] Both strategies had in common the problem of the delicate oxidation, in order not to over oxidizing to the nitro group.…”

Section: Scheme 17mentioning

confidence: 99%

Shape‐Switchable Azo‐Macrocycles

et al. 2009

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The synthesis of four shape‐switchable macrocycles comprising different peripheral substituents is described. The macrocycles 1–4 consist of m‐terphenyl semicircles interlinked by two azo joints. These macrocycles were assembled from nitro‐functionalized m‐terphenyl moieties through reductive dimerization. The semicircles were assembled through Suzuki cross‐coupling reactions. The molecular weights of the macrocycles were determined by vapour pressure osmometry, because mass spectrometry failed in the cases of 2 and 3. The E → Z photoisomerization reactions were analysed by UV/Vis spectroscopy complemented by 1H NMR studies. A very slow thermal back‐reaction indicated considerable stabilization of the Z isomer. The reduced efficiency of the thermal back‐reaction probably arises from the reduced degree of freedom due to the mechanical interlinking of the two azo groups. The photostationary state consisted of all‐Z (85 %) and all‐E isomers (15 %). The E → Z transformation induced by irradiation displayed simple exponential kinetics, which indicates pairwise switching of the two azo groups in a macrocycle, at least on the timescale under investigation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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“…A series of reactions with phosphine ligands showed clearly that electron-deficient phosphine ligands gave the O adduct 3 a preferentially ( Table 2, entries 1-4). Encouraged by these results, we tested other electrondeficient ligands and found that PPh(OPh) 2 and P(OPh) 3 gave 3 a with good selectivity (Table 2, entries 5, 6, and 8). Moreover, when 10 mol % of P(OPh) 3 was used, 3 a was obtained almost exclusively (Table 2, entry 9).…”

mentioning

confidence: 88%