Abstract
Indoles are converted into α-carbolines in four steps by acylation at C-3, Boc-protection, olefination of the resulting 3-indolyl aldehydes or ketones to give N-Boc-3-indolyl alkenyl oxime O-methyl ethers, which upon heating to 240 °C under microwave irradiation undergo loss of the Boc-group, and 6π-electrocyclization to α-carbolines, following aromatization by loss of methanol (11 examples, 30–90% yield).
Highlights
Indoles are converted into R-carbolines in four steps by acylation at C-3, Boc-protection, olefination of the resulting 3-indolyl aldehydes or ketones to give N-Boc-3-indolyl alkenyl oxime O-methyl ethers, which upon heating to 240 °C under microwave irradiation undergo loss of the Boc-group, and 6π-electrocyclization to R-carbolines, following aromatization by loss of methanol (11 examples, 30À90% yield)
Routes for the construction of the R-carboline nucleus are of interest, but unlike their β-carboline counterparts that are almost invariably prepared from tryptophan or tryptamine derivatives, there is no main synthetic access to the isomeric R-carbolines
R-carbolines have been obtained from 2-aminoindoles,14À16 by a variation of the GraebeÀUllmann synthesis of
Summary
A New Route to r‐Carbolines Based on 6π-Electrocyclization of Indole-3-alkenyl Oximes Indoles are converted into R-carbolines in four steps by acylation at C-3, Boc-protection, olefination of the resulting 3-indolyl aldehydes or ketones to give N-Boc-3-indolyl alkenyl oxime O-methyl ethers, which upon heating to 240 °C under microwave irradiation undergo loss of the Boc-group, and 6π-electrocyclization to R-carbolines, following aromatization by loss of methanol (11 examples, 30À90% yield). We were attracted by the possibility of developing a more general route based on a 6π-electrocyclic process, and we report our initial results.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
