An unexpected borylation of organic halides with a silyborane in the presence of an alkoxy base has been observed. This formal nucleophilic boryl substitution can be applied to a broad range of substrates with high functional group compatibility. Even sterically hindered aryl bromides afforded the corresponding boryl compounds in high yields. Preliminary mechanistic studies indicated that this boryl substitution is promoted by neither transition-metal contamination nor a radical-mediated process.
A borylative exo-cyclization of alkenyl halides has been reported. The reaction includes the regioselective addition of a borylcopper(I) intermediate to unactivated terminal alkenes, followed by the intramolecular substitution of the resulting alkylcopper(I) moiety for the halide leaving groups. Experimental and theoretical investigations of the reaction mechanism have also been described. This reaction provides a new method for the synthesis of alkylboronates containing strained cycloalkyl structures from simple starting materials.
In the last 10 years, extensive earthquake swarms have occurred intermittently in the region east of Izu Peninsula, central Japan. In July 1989 an active swarm again took place off Ito City, and among all past activities, it was nearest to land and shallowest. This activity eventually became a weak submarine eruption, the first of its kind in this region. Associated with this event, a borehole tiltmeter at 92 m depth, installed several kilometers from the source area, detected distinct continuous tilt change with the following features: (1) Tilt of 20 μrad was observed within 1 week preceding the eruption. (2) Tilt change showed a good correlation to swarm activity. (3) No obvious coeruption tilt change was observed. On the basis of the tilt record and swarm distribution, we constructed a dislocation model to interpret the seismovolcanic activity. The model consists of two tensile faults, each of which corresponds to magma intrusions in May and July, and a right‐lateral reverse fault representing the largest earthquake (M5.5) at 1109 LT on July 9. This model can simulate not only the above tilt data but also the record of a nearby dilatometer, the results from daily laser distance measurements and daily Global Positioning System monitoring, as well as results from other conventional distance surveys and leveling surveys in the surrounding region. From this model, we conclude that the intersection of the shear fault with the tensile fault caused magma to come up into soft sedimentary layers at the seabottom, creating a lava dome. Later an instability brought about a magma‐phreatic explosion which did not generate any substantial crustal deformations at deeper levels.
The enantioselective 1,1-diarylation of terminal alkenes is reported herein enabled by the combination of palladium catalysis with a chiral anion phase-transfer strategy. The reaction of substituted benzyl acrylates with aryldiazonium salts and arylboronic acids gave the corresponding 3,3-diaryl propanoates in moderate to good yields and high enantioselectivies (up to 98:2 er). Substituents on the benzyl acrylate and chiral anion phase-transfer catalyst significantly affect the enantioselectivity, and multidimensional parameterization identified correlations suggesting structural origins for high stereocontrol.
The Miyakejima observation network had been constructed by the National Research Institute for Earth Science and Disaster Prevention mainly until early 1999. This observation network has provided the crustal deformation data by tiltmeters and GPS and the seismic data by short-period and broadband seismometers in association with the 2000 Miyakejima eruption. The subsurface magma movement at the first stage of the present activity, during the period from June 26 to 27, was successfully detected mainly by the tilt measurements. The tilt change observed at five stations indicates the migration of magmas from the eastern part of Miyakejima to the western part. The most distinctive phenomenon appearing after the first stage is tilt steps, which started on July 8 with the first eruption from the summit crater. Each tilt step indicates an abrupt uplift of the summit area. These tilt steps continued until the eruption of August 18, which is the largest eruption up to early September, 2000. 45 tilt steps in total were observed in this period. The seismic data show a variety of seismograms including VT (volcano-tectonic) earthquakes, LF (low frequency) earthquakes and volcanic tremor. At the time of the tilt steps, very long period events with predominant periods of about 100 s were detected by the broadband seismometers. As the activity has still continued, this report summarizes the observation during June, July, and August, 2000.
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