Quinone photochemistry. A general synthesis of acylhydroquinones

The synthesis of dihydroxy ketones such as 1 is usually accomplished by a sequence involving Friedel-Crafts acylation and hydrolysis.

A photochemical Alternative to the Friedel-Crafts Reaction

The Friedel-Crafts reaction, a widely used reaction in both industrial and academic laboratories, produces several byproducts which must be handled as pollutants. An alternative which involves the photochemically-mediated reaction of an aldehyde with a quinone is described. This alternative chemistry can be applied to direct syntheses of the ring systems of the benzodiazepines and benzoxepins

Stellar Stream and Halo Structure in the Andromeda Galaxy From a Subaru/Hyper Suprime-Cam Survey

We present wide and deep photometry of the northwest part of the halo of the Andromeda galaxy (M31) using Hyper Suprime-Cam on the Subaru Telescope. The survey covers 9.2 deg$^{2}$ field in the $g$, $i$, and $NB515$ bands and shows a clear red giant branch (RGB) of M31's halo stars and a pronounced red clump (RC) feature. The spatial distribution of RC stars shows a prominent stream feature, the North Western (NW) Stream, and a diffuse substructure in the south part of our survey field. We estimate the distances based on the RC method and obtain $(m-M)$ = 24.63$\pm 0.191$(random)$\pm0.057$(systematic) and 24.29$\pm 0.211$(random)$\pm0.057$(systematic) mag for the NW stream and diffuse substructure, respectively, implying that the NW Stream is located behind M31, whereas the diffuse substructure is located in front. We also estimate line-of-sight distances along the NW Stream and find that the south part of the stream is $\sim$20 kpc closer to us relative to the north part. The distance to the NW Stream inferred from the isochrone fitting to the color-magnitude diagram favors the RC-based distance, but the TRGB-based distance estimated for $NB515$-selected RGB stars does not agree with it. The surface number density distribution of RC stars across the NW Stream is found to be approximately Gaussian with a FWHM of $\sim$25 arcmin (5.7 kpc), with a slight skew to the south-west side. That along the NW Stream shows a complicated structure including variations in number density and a significant gap in the stream.Comment: 24 pages, 18 figures, accepted for publication in Ap