Surprising acidity for the methylene of 1,3-indenocorannulenes?

• Shi Liu,
• Märt Lõkov,
• Sofja Tshepelevitsh,
• Ivo Leito,
• Kim K. Baldridge and
• Jay S. Siegel

Beilstein J. Org. Chem. 2024, 20, 3144–3150, doi:10.3762/bjoc.20.260

• ; Loschmidt group element; molecular graph; Introduction A classic textbook tetrad linking hydrocarbon acidity to aromatic stabilization energy comprises cyclopentadiene (CpH), indene (InH), fluorene (FlH), and diphenylmethane (DPMH) [1][2], with pKa values in DMSO equal to 18 [3], 20.1 [3], 22.6 [3], and

• benzene [7][8]. Furthermore, the trend of pKa values for CpH, InH, and FlH correlates with the reduction of the aromatic stabilization energy for the anion across the series [1][2]. At first glance, this model supports the notion that the relative pKa values of cyclopentadienes embedded in polynuclear

• GAMESS [36] and has also contributed to Gaussian software packages, in this work the G09 ES64L-G09RevE.01 version [37] of the latter was used. Aromatic stabilization energy across a series of small aromatics (upper); graphical depiction of the BFC/FIC acidity quandry (lower). Clar–Loschmidt graphs

Click chemistry towards thermally reversible photochromic 4,5-bisthiazolyl-1,2,3-triazoles

• Chenxia Zhang,
• Kaori Morinaka,
• Mahmut Kose,
• Takashi Ubukata and
• Yasushi Yokoyama

Beilstein J. Org. Chem. 2019, 15, 2161–2169, doi:10.3762/bjoc.15.213

• electron-withdrawing cyano groups than when they are electron-donating methoxy groups. Keywords: aromatic stabilization energy; diarylethene; ruthenium(I) catalysed Huisgen cyclization; terarylene; thermally reversible photochromism; Introduction Diarylethenes are one of the most widely investigated

• among the photochromic families [1][2][3]. They are known to show thermally irreversible photochromism. However, some of them are thermally reversible [4]: (1) when the aromatic stabilization energy of the aromatic rings is large [5]; (2) when the substituent groups on the ring-closing carbon atoms are

• related families of diarylethenes, are largely thermally reversible [10][12] although some are irreversible when the aromatic stabilization energy of the aromatic rings is small [11]. Their syntheses are usually carried out by the sequential construction of the central aromatic ring at the final stage [10