A metal-free and oxidant-free protocol for oxidative coupling of quinoxalin-2(1H)-ones with diarylphosphine oxides and pyrroles via electrochemical dehydrogenation has been reported. A broad range of C3-functionalized products were obtained in good to excellent yields.[a] Dr.

Yb(OTf) 3 catalyzed synthesis of pyrazoles by cyclization of 1,3-diarylpropynones with carbazates was reported. In the presence of K 2 S 2 O 8 /TBAI as catalyst, α,β-alkynic hydrazone was obtained through the reactions from the same starting materials in up to 97% yields. Mechanistic studies indicated that propargyl hydrazone was not involved in pyrazole formation. The aggregation-induced emission (AIE) characteristics of the pyrazoles were explored, demonstrating potential applications in the luminophoric materials.

Vector quantized diffusion (VQ-Diffusion) is a powerful generative model for textto-image synthesis, but sometimes can still generate low-quality samples or weakly correlated images with text input. We find these issues are mainly due to the flawed sampling strategy. In this paper, we propose two important techniques to further improve the sample quality of VQ-Diffusion. 1) We explore classifier-free guidance sampling for discrete denoising diffusion model and propose a more general and effective implementation of classifier-free guidance. 2) We present a high-quality inference strategy to alleviate the joint distribution issue in VQ-Diffusion. Finally, we conduct experiments on various datasets to validate their effectiveness and show that the improved VQ-Diffusion suppresses the vanilla version by large margins. We achieve an 8.44 FID score on MSCOCO, surpassing VQ-Diffusion by 5.42 FID score. When trained on ImageNet, we dramatically improve the FID score from 11.89 to 4.83, demonstrating the superiority of our proposed techniques. The code is released at https://github.com/microsoft/VQ-Diffusion.Preprint. Under review.

A route to indeno[1,2-b]indole by self-condensation is reported; its synthetic utility has been demonstrated by gram-scale synthesis and potential fluorescence applications.

A new efficient approach to highly substituted fluorenes has been presented by reacting 9-aryl-9-fluorenols with 1,1-diarylethylenes. These reactions were catalyzed by Sc(OTf) 3 and provided a wide variety of the corresponding products in excellent yields (up to 99 % yield). In addition, the initial photophysical property evaluation of certain products may inspire the development of potential OLEDs materials.