Cyclic Homo- and Heterohalogen Di-λ3-diarylhalonium Structures.

In the context of the ever-growing interest in the cyclic diaryliodonium salts, this work presents synthetic design principles for a new family of structures with two hypervalent halogens in the ring. The smallest bis-phenylene derivative, [(C6H4)2I2]2+, was prepared through oxidative dimerization of a precursor bearing the ortho-disposed iodine and trifluoroborate groups. We also report, for the first time, the formation of cycles containing two different halogen atoms. These present two phenylenes linked by hetero-(I/Br) or -(I/Cl) halogen pairs. This approach was also extended to the cyclic bis-naphthylene derivative [(C10H6)2I2]2+. The structures of these bis-halogen(III) rings were further assessed through X-ray analysis. The simplest cyclic phenylene bis-iodine(III) derivative features the interplanar angle of ∼120°, while a smaller angle of ∼103° was found for the analogous naphthylene-based salt. All dications form dimeric pairs through a combination of π-π and C-H/π interactions. As the largest member of the family, a bis-I(III)-macrocycle was also assembled using the quasi-planar xanthene backbone. Its geometry enables the two iodine(III) centers to be bridged intramolecularly by two bidentate triflate anions. In a preliminary manner, the interaction of the phenylene- and naphthalene-based bis-iodine(III) dications with a new family of rigid bidentate bis-pyridine ligands was studied in solution and the solid state, with an X-ray structure showing the chelating donor bonding to just one of the two iodine centers.

Convolutional neural network assistance significantly improves dermatologists' diagnosis of cutaneous tumours using clinical images.

BACKGROUND: Convolutional neural networks (CNNs) have demonstrated expert-level performance in cutaneous tumour classification using clinical images, but most previous studies have focused on dermatologist-versus-CNN comparisons rather than their combination. The objective of our study was to evaluate the potential impact of CNN assistance on dermatologists for clinical image interpretation. METHODS: A multi-class CNN was trained and validated using a dataset of 25,773 clinical images comprising 10 categories of cutaneous tumours. The CNN's performance was tested on an independent dataset of 2107 images. A total of 400 images (40 per category) were randomly selected from the test dataset. A fully crossed, self-control, multi-reader multi-case (MRMC) study was conducted to compare the performance of 18 board-certified dermatologists (experience: 13/18 ≤ 10 years; 5/18＞10 years) in interpreting the 400 clinical images with or without CNN assistance. RESULTS: The CNN achieved an overall accuracy of 78.45% and kappa of 0.73 in the classification of 10 types of cutaneous tumours on 2107 images. CNN-assisted dermatologists achieved a higher accuracy (76.60% vs. 62.78%, P < 0.001) and kappa (0.74 vs. 0.59, P < 0.001) than unassisted dermatologists in interpreting the 400 clinical images. Dermatologists with less experience benefited more from CNN assistance. At the binary classification level (malignant or benign), the sensitivity (89.56% vs. 83.21%, P < 0.001) and specificity (87.90% vs. 80.92%, P < 0.001) of dermatologists with CNN assistance were also significantly improved than those without. CONCLUSIONS: CNN assistance improved dermatologist accuracy in interpreting cutaneous tumours and could further boost the acceptance of this new technique.

Exploring benzylic gem-C(sp3)-boron-silicon and boron-tin centers as a synthetic platform.

A stepwise build-up of multi-substituted Csp3 carbon centers is an attractive, conceptually simple, but often synthetically challenging type of disconnection. To this end, this report describes how gem-α,α-dimetalloid-substituted benzylic reagents bearing boron/silicon or boron/tin substituent sets are an excellent stepping stone towards diverse substitution patterns. These gem-dimetalloids were readily accessed, either by known carbenoid insertion into C-B bonds or by the newly developed scalable deprotonation/metallation approach. Highly chemoselective transformations of either the C-Si (or C-Sn) or the C-B bonds in the newly formed gem-Csp3 centers have been achieved through a set of approaches, with a particular focus on exploiting the synthetically versatile polarity reversal in organometalloids by λ3-aryliodanes. Of particular note is the metal-free arylation of the C-Si (or C-Sn) bonds in such gem-dimetalloids via the iodane-guided C-H coupling approach. DFT calculations show that this transfer of the (α-Bpin)benzyl group proceeds via unusual [5,5]-sigmatropic rearrangement and is driven by the high-energy iodine(iii) center. As a complementary tool, the gem-dimetalloid C-B bond is shown to undergo a potent and chemoselective Suzuki-Miyaura arylation with diverse Ar-Cl, thanks to the development of the reactive gem-α,α-silyl/BF3K building blocks.

Iodane-Guided ortho C-H Allylation.

A metal-free C-H allylation strategy is described to access diverse functionalized ortho-allyl-iodoarenes. The method employs hypervalent (diacetoxy)iodoarenes and proceeds through the iodane-guided "iodonio-Claisen" allyl transfer. The use of allylsilanes bearing electron-withdrawing functional groups unlocks the functionalization of a broad range of substrates, including electron-neutral and electron-poor rings. The resulting ortho-allylated iodoarenes are versatile building blocks, with examples of downstream transformation including a concise synthesis of the experimental antimitotic core of Dosabulin. DFT calculations shed additional light on the reaction mechanism, with notable aspects including the aromatic character of the transition-state structure for the [3,3] sigmatropic rearrangement, as well as the highly stereoconvergent nature of the trans-product formation.

The Power of Iodane-Guided C-H Coupling: A Group-Transfer Strategy in Which a Halogen Works for Its Money.

Hypervalent organoiodane reagents are ubiquitous in organic synthesis, both as oxidants and as electrophilic group-transfer agents. In addition to these hallmark applications, a complementary strategy is gaining momentum that exploits the ability of λ3 -iodanes to undergo iodine-to-arene group transfer, for example, via iodonio-Claisen-type rearrangement processes. This Minireview discusses recent advances in the use of this method to access a variety of the C-H-functionalized iodoarenes. While Section 2 is focused on the ortho C-H propargylation, allylation, and the more unusual para C-H benzylation, Section 3 is devoted to the C-arylation of enol and phenol substrates. The accompanying discussion includes mechanistic considerations and goes into the synthetic applications of the final iodoarene cores. The Minireview concludes with further conceptual extensions of the method, including the use of non-conventional coupling partners (for example, cyanoalkylation), improved access to λ3 -iodane building blocks, and the development of iterative approaches to polysubstituted iodoarenes.

Structural brain abnormalities in patients with primary open-angle glaucoma: a study with 3T MR imaging.

PURPOSE: We examined changes of the central nervous system in patients with advanced primary open-angle glaucoma (POAG). METHODS: The clinical observational study included 15 patients with bilateral advanced POAG and 15 healthy normal control subjects, matched for age and sex with the study group. Retinal nerve fiber layer (RNFL) thickness was measured by optical coherence tomography (OCT). Using a 3-dimensional magnetization-prepared rapid gradient-echo sequence (3D-MP-RAGE) of magnetic resonance imaging (MRI) and optimized voxel-based morphometry (VBM), we measured the cross-sectional area of the optic nerve and optic chiasm, and the gray matter volume of the brain. RESULTS: Patients in the POAG group compared to the subjects in the control group showed a significant (P < 0.001) decrease in the bilateral gray-matter volume in the lingual gyrus, calcarine gyrus, postcentral gyrus, superior frontal gyrus, inferior frontal gyrus, and rolandic operculum, as well as in the right cuneus, right inferior occipital gyrus, left paracentral lobule, and right supramarginal gyrus. Patients in the study group showed a significant increase in the bilateral gray matter volume in the middle temporal gyrus, inferior parietal gyrus, and angular gyrus, and in the left gray matter volume in the superior parietal gyrus, precuneus, and middle occipital gyrus. In addition, the cross-sectional area of the optic nerve and optic chiasm, and RNFL thickness were significantly decreased in the POAG group. CONCLUSIONS: In patients with POAG, three-dimensional MRI revealed widespread abnormalities in the central nervous system beyond the visual cortex.