Conditions for metalation of a variety of cyclic vinylethers and reaction of the resulting carbanions with electrophiles are described. Effects of the vinylether structure on the relative rates of metalation are discussed. Applications of this methodology to the construction of various types of carbonyl compounds are presented.
C-2/C-3 Annulation and C-2 Alkylation of Indoles with 2-Alkoxycyclopropanoate Esters
作者:Barbora Bajtos、Ming Yu、Hongda Zhao、Brian L. Pagenkopf
DOI:10.1021/ja067821+
日期:2007.8.1
reaction between various indoles and 2-alkoxycyclopropanoate esters is reported. Both high efficiency and complete stereochemical control were observed in some cases with this annulation process. A single stereocenter on the cyclopropane controls the diastereoselective formation of up to four new stereocenters. A different reaction course was observed with 3-substitutedindole substrates, and an intervening
An effective synthesis of (E)-4-oxo-5-hexenals 6 and the acetals 5 starting from ethyl 2-alkoxy-1-cyclopropanecarboxylates 1a-d is presented. The acid-induced ring opening of the cyclopropanecarboxylates 1a, b, followed by phosphorylmethylation or the phosphorylmethylation of the ester 1c followed by ring opening leads to the 5-acetal of 2,5-dioxopentylphosphonate 4. The Horner-Emmons olefination of 4 with various aldehydes produces the title compounds.
A Powerful New Strategy for Diversity-Oriented Synthesis of Pyrroles from Donor−Acceptor Cyclopropanes and Nitriles
作者:Ming Yu、Brian L. Pagenkopf
DOI:10.1021/ol036180+
日期:2003.12.1
Lewisacid activated donor-acceptor cyclopropanes react with aliphatic, aromatic, and alpha,beta-unsaturated nitriles in a novel cascade [3 + 2] dipolarcycloaddition, dehydration, and tautomerization sequence to afford pyrroles in moderate to excellent overall yield. This cost-effective and regiospecific method is ideally suited for the preparation of combinatorial libraries. [reaction: see text]
Synthesis of 2,2‘-Bipyrroles and 2,2‘-Thienylpyrroles from Donor−Acceptor Cyclopropanes and 2-Cyanoheteroles
作者:Ming Yu、G. Dan Pantos、Jonathan L. Sessler、Brian L. Pagenkopf
DOI:10.1021/ol049857h
日期:2004.3.1
[reaction: see text] Two new series of 2,2'-bipyrroles and 2,2'-thienylpyrroles have been prepared by trimethylsilyl trifluoromethanesulfonate (TMSOTf)-mediated reaction of donor-acceptor cyclopropanes with 2-cyanopyrroles and 2-cyanothiophene, respectively. This method opens the door toward a wide variety of unsymmetrical bipyrroles and thienylpyrroles.