The synthesis of a series of 1,2‐diamino‐o‐carboranes (1–4) is reported. The molecular structures of these diamino‐o‐carboranes are remarkable as the inner‐cluster C−C bonds are all ultra‐long (162.7–193.1 pm) and vary substantially with small variations in the substituents. The results of quantum mechanical investigations suggest that the origin of the bond elongation is significant in‐plane negative hyperconjugation of lone pairs of the nitrogen substituents with the σ* orbitals of the C−C bonds in o‐carboranes.

1,2‐Diamino‐o‐carborane mit außergewöhnlich langen C‐C‐Bindungen (bis 193 pm) wurden synthetisiert. In ihrer Zuschrift auf S. 1411 erklären Z. Li, X.‐Q. Xiao et al. die beobachtete Streckung mit einer negativen Hyperkonjugation zwischen den freien Elektronenpaaren der Stickstoffatome und dem σ*C‐C‐Orbital des o‐Carborans. Im Bild halten zwei Kraniche ein solches Molekül, wobei sie dessen C‐C‐Bindung bis fast zum Zerreißen dehnen. (Passenderweise fliegen sie dabei über die “Broken Bridge” bei Hangzhou.)

PurposeProgrammed death-ligand 1 (PD-L1) is found to be overexpressed in non-small cell lung cancer. The present study intended to evaluate the status of PD-L1 expression in patients with resection and recurrent lung adenocarcinoma.Patients and methodsMatched resection and recurrent tumor samples were harvested from 65 lung adenocarcinoma patients. Immunohistochemistry was used to evaluate the status of PD-L1 expression. Kaplan–Meier method was used for survival analysis.ResultsA total of 65 patients of lung adenocarcinoma were enrolled. They underwent complete resection and had recurrence after adjuvant treatment. PD-L1 expression was identified in 43.1% (28/65) of resection samples vs 55.4% (36/65) of recurrent samples. Ten patients shifted from negative to positive, whereas another two samples showed the opposite. Patients with PD-L1 expression showed worse disease-free survival than the PD-L1-negative counterparts. The expression of PD-L1 in recurrent samples was a significant favorable factor for epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) (11.2 vs 8.2 months, P=0.030).ConclusionThe status of PD-L1 expression may alter between resection and recurrent samples. Also, the status of PD-L1 expression after recurrence is a better prognostic factor for EGFR-TKIs.

A series of 1,2-N-substituted o-carboranes were obtained. Ultra-long C–C distances were found in the secondary-amino o-carboranes 3. The relationship between C–C bond lengths and the electron effects of the benzyl groups was discussed.

Main observation and conclusion The steric and electronic properties of N‐heterocyclic carbenes (NHCs) can be modified by the exocyclic substituents at the nitrogen atoms, by 1—3 atoms’ replacements of the five‐membered imidazolium skeleton and by the changes of the backbones. Herein, we report the usage of nido‐C2B9 carborane anions as the backbones of NHCs. Stirring the mixture of secondary amino o‐carboranes (1b—1e), triethyl orthoformate and HBF4∙Et2O results in the unexpected cage‐opening of o‐carboranes to afford the nido‐C2B9 carborane anions supported N‐heterocyclic carbene precursors (4b—4e). Deprotonation of 4b with sodium hexamethyldisilazide at −78 oC affords the N‐heterocyclic carbene ligand, which was used to form an Au(I) NHC complex (5). DFT calculations revealed a high‐lying lone pair orbitals of the carbene ligands, predicting their strong σ‐donating abilities.