Brønsted acid-mediated annulations of pyrroles featuring N-tethered α,β-unsaturated ketones and esters: Total syntheses of (±)-tashiromine and (±)-indolizidine 209I
作者:Wesley J. Olivier、Michael G. Gardiner、Alex C. Bissember、Jason A. Smith
DOI:10.1016/j.tet.2018.04.067
日期:2018.9
tetrahydroindolizines and tetrahydropyrrolo[1,2-a]azepines via Brønsted acid-mediated annulation of pyrroles featuring N-tethered α,β-unsaturated esters. In addition, the Brønsted acid-catalyzed cyclization of pyrroles featuring pendant α,β-unsaturatedketones was applied to complete total syntheses of the indolizidine alkaloids (±)-tashiromine and (±)-indolizidine 209I.
When 1-allylpyrrole was subjected to hydroformylation conditions with Rh-4(CO)(12) as the catalyst precursor, at 120 atm total pressure, at 20 and 100 degrees C, 5,6-dihydroindolizine was found unexpectedly, together with the expected branched aldehyde, the linear isomer being obtained in traces amounts only. An annulation via a nucleophilic attack of the pyrrole C2 carbon atom on the carbonyl group of the linear aldehyde, followed by dehydration of the intermediate alcohol, possibly generates the indolizine structure. (C) 2000 Elsevier Science S.A. All rights reserved.
Compounds of formula (1) are described wherein Ar is an optionally substituted aryl, heteroaryl, aralkyl, heteroaralkyl or alkyl group, X is a nitrogen atom or a C(R1a) group, n is zero or the integer 1 or 2 and R, R?1, R2, R3 and R4¿ are substituents defined in the specification. The compounds are able to inhibit the activity of Class 1 receptor tyrosine kinases and are of use in the treatment of hyperproliferative disorders such as psoriasis.
The influence of chiral auxiliaries and catalysts on the selectivity of intramolecular conjugate additions of pyrrole to N-tethered Michael acceptors
作者:Martin G. Banwell、Daniel A. S. Beck、Jason A. Smith
DOI:10.1039/b312552a
日期:——
A series of pyrroles incorporating N-tethered acrylates and related groups has been prepared and examined for their capacity to undergo intramolecular Michael addition reactions to form, in a diastereo- or enantio-selective fashion, the corresponding 8-substituted tetrahydroindolizidine or homologues thereof.