We herein describe the syntheses and characterization of extended germa[N]pericyclynes, which are macrocycles composed of germanium–butadiyne units. The obtained novel extended germa[4]–[8]pericyclynes were characterized by X-ray crystallography, UV-Vis spectroscopy, fluorescence and phosphorescence emission spectroscopy, and cyclic voltammetry, and exhibited characteristic absorptions and emissions. Density functional theory (DFT) calculations suggested smaller HOMO–LUMO gap energy compared to that of general germapericyclynes.

The synthesis of functional cyclic nitrones via [3+2] cycloadditions of allenamide-derived nitrosoallenes with carbonyl/nitrile compounds, including ketones, esters, and nitriles, is presented herein. Rapid carbon–carbon, carbon–oxygen, and carbon–nitrogen bond formations were achieved with in situ prepared nitrosoallenes, and densely substituted oxacyclic and carbocyclic nitrones containing tetrasubstituted carbon centers were successfully synthesized. The spirocyclic nitrone products synthesized from cyclic dicarbonyl compounds underwent the unique skeletal rearrangements to cyclic α-ketonitrones.

This paper reports nitrosoallene-mediated synthesis of α-substituted enoximes. Nucleophilic substitution of nitrosoallenes, a novel chemical species prepared from allenyl N-hydroxysulfonamides, afforded α-functionalized enoximes. Introduction of various nucleophiles proceeded smoothly to form C–N, C–O, C–S, C–F, and C–C bonds in the presence of azodicarboxylates.

Synthesis and optical properties of skipped polyynes comprising germanium–acetylene units are presented. The prepared germanium polymers were investigated by UV-vis, fluorescence, and phosphorescence spectroscopy and DFT calculations. The optical properties were compared to those of cyclic compounds, germa[N]pericyclynes. The unique fluorescence and phosphorescence behaviours of acyclic polymers were observed.

The stepwise syntheses of germa[N]pericyclynes, including [5]pericyclynes, and their characterization are described. The yields of germa[4] and [8]pericyclynes were improved significantly compared to those obtained in previous studies. The routes reported herein afforded the novel germa[5] and [10]pericyclynes, which were characterized by X-ray crystallography, UV-Vis spectroscopy, and fluorescence emission spectroscopy. A unique fluorescence emission was observed for the large germa[10]pericyclyne ring.

Regioselective rapid triazole syntheses at low temperature are described. Organic azides and propargyl cations generated by acids gave fully substituted 1H-1,2,3-triazoles. Most reactions could be performed in 5 min at not only rt but also −90 °C. Both terminal and internal alkynes were acceptable, and the sterically bulky substituents could afford the products smoothly. Various types of three-component coupling reactions were demonstrated, and the presence of allenylaminodiazonium intermediates was indicated.

An efficient synthesis of α,β-unsaturated alkylimines at low temperature using azides has been developed. Carbocations generated from allyl alcohols helped achieve a rapid conversion under mild conditions with azides to afford reactive α,β-unsaturated imines. Hydroxy or alkoxy groups are essential for these transformations, and utilizing readily accessible allyl alcohols gave a wide extension of substrates. The efficiency of this novel method is demonstrated in the total synthesis of an iminium ant venom alkaloid.

Double nucleophilic N-alkylation of α-oxime-esters, affording N,N-dialkyl-α-amino acids is herein described. Grignard reagents accomplished double N-alkylations via umpolung and various N,N-dialkylated α-amino acids were successfully synthesized in 15 min. Both electron-withdrawing sulfonyl groups and electron-donating silyl and methyl groups on oximes were available. Alkylmagnesium species and (E)-configuration of α-oxime-ester were essential to this cascade reaction.

The stepwise syntheses of germa[N]pericyclynes, including [5]pericyclynes, and their characterization are described. The yields of germa[4] and [8]pericyclynes were improved significantly compared to those obtained in previous studies. The routes reported herein afforded the novel germa[5] and [10]pericyclynes, which were characterized by X-ray crystallography, UV-Vis spectroscopy, and fluorescence emission spectroscopy. A unique fluorescence emission was observed for the large germa[10]pericyclyne ring.

We herein describe the syntheses and characterization of extended germa[N]pericyclynes, which are macrocycles composed of germanium–butadiyne units. The obtained novel extended germa[4]–[8]pericyclynes were characterized by X-ray crystallography, UV-Vis spectroscopy, fluorescence and phosphorescence emission spectroscopy, and cyclic voltammetry, and exhibited characteristic absorptions and emissions. Density functional theory (DFT) calculations suggested smaller HOMO–LUMO gap energy compared to that of general germapericyclynes.