No abstract

Experimentally, the density profile in the magnetic nozzle of a helicon antenna based plasma device is seen to be modified from being centrally peaked to that of hollow nature as the external magnetic field is increased. It occurs above a characteristic field value when the ions become magnetized in the expansion chamber. The density profile in the source chamber behind the nozzle, however, remains peaked on-axis irrespective of the magnetic field. The electron temperature there is observed to be hollow and this nature is carried to the expansion chamber along the field line. In the electron energy distribution near the off axis peak location, a high energy tail exists. Rotation of these tail electrons in the azimuthal direction due to the gradient-B drift in the expansion chamber leads to an additional off-axis ionization and forms the hollow density profile. It seems that if the ions are not magnetized, then the off-axially produced additional plasma is not confined and the density profile retains the on-axis peak nature. The present experiment successfully demonstrates how the knowledge of the ion magnetization together with tail electrons significantly contributes to the design of an efficient helicon plasma based thruster.

Diversity oriented one-pot synthesis of cyclohepta[b]indoles, indolotropones, and tetrahydrocarbazoles (THCs) have been reported. Readily accessible 3-(2-aminophenyl)-5-hexenyn-3-ols under a one-pot trimetallic orthogonal catalysis furnish tetrahydrocyclohepta[b]indoles, and a one-pot quadruple reaction sequence of the enynols generates dihydrocyclohepta[b]indoles and indolotropones. During this study, formation of THCs was realized to be a reason for the yield loss in certain cases, this observation led to the development of a one-pot bimetallic approach for the synthesis of 1,3-disubstituted THCs.

We describe the first atropselective Suzuki−Miyaura cross-coupling of β-keto enol triflates to access axially chiral (Z)diarylmethylidene indanones (DAIs). The chemical, physical, and biological properties of DAIs are unknown, despite their being structurally similar to arylidene indanones, primarily due to the lack of racemic or chiral methods. Through this work, we demonstrate a general and efficient protocol for the racemic as well as the atropselective synthesis of (Z)-DAIs. An unusual intramolecular Morita−Baylis−Hillman reaction is utilized for the Z-selective synthesis of β-keto enol triflates. ■ ASSOCIATED CONTENT * sı Supporting InformationThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.orglett.1c01671.Experimental details and characterization data for all new compounds ( 1 H NMR, 13 C NMR) (PDF)Accession CodesCCDC 2057339 and 2057498 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk

An efficient palladium-catalyzed intramolecular Trost–Oppolzer type Alder-ene strategy was developed for the synthesis of carbazoles and cyclopenta­[b]­indoles from easily accessible­(3-allyl-1H-indol-2-yl)­methyl acetates. This strategy was extended for the synthesis of naphthalenes and dibenzobenzofurans as well. In addition, a short synthesis of antibacterial and antifungal natural product glycozoline and its analogues was also achieved.