An Iron-Promoted Aldehyde−Diene Cyclocoupling Reaction

Abstract

A stereospecific intramolecular iron tricarbonyl-promoted aldehyde-diene cyclocoupling reaction was investigated by using simple substrates 6 and more complicated substrates 30a/30b. Demetalation of the initial products converts all complexed dienes to their pure organic counterparts. In addition, the nickel-catalyzed carbonyl-ene reaction and the Prins reaction were investigated with two different substrates.

Iron(0) Tricarbonyl Complexes of Microbially Derived Cyclohexadiene Ligands Containing Quaternary Stereocenters

“…We first attempted the direct complexation of 7 by treatment with Fe 2 (CO) 9 in THF, but this resulted only in intractable mixtures. We therefore derivatized 7 as the corresponding methyl ester 8 by treatment with trimethylsilyldiazomethane in methanol/benzene.…”

“…We therefore derivatized 7 as the corresponding methyl ester 8 by treatment with trimethylsilyldiazomethane in methanol/benzene. 8c The resultant crude ester was then directly treated with Fe 2 (CO) 9 to furnish endo complex 9 as the sole isomer (Scheme 4).…”

“…Numerous examples of tricarbonyl(cyclohexadiene)iron complexes possessing a quaternary center on the cyclohexadiene ligand are known. However, the majority of these are assembled by ligand modification post-complexation, 9 often by a [η 4 ]→[η 5 ] + →[η 4 ] sequence. 10 Complexation of a tricarbonyliron fragment to a cyclohexadiene ligand with a preexisting quaternary center is much less common.…”

Stereocontrolled Intramolecular Iron-mediated Diene/Vinyl Ether Cyclocoupling Reactions

“…Our group has developed a stereocontrolled intramolecular iron-mediated diene/olefin cyclocoupling reaction, equivalent to a [6 + 2] ene reaction, which forms spirolactones, spirothiolactones and spirolactams under thermal or photothermal conditions (eq , Y = CH 2 , Z = CH 3 ) . We recently extended this reaction to include aldehydes ( 1 , Y = O) as the 2π component, which affords hydroxyl substituted spirolactams ( 2 , Z = OH) that embody in the organic moiety key structural features of natural products such as the spirostaphylotrichins . The work described in this report aims to further expand the scope of the cyclocoupling reaction to include vinyl ethers as the 2π component, which would result in spirocyclic molecules having (protected) hydroxymethyl side chains.…”

“…Previously reported aldehydes 3a and 3b were each reacted with (methoxymethyl)triphenyl-phosphorane to afford methoxy vinyl ethers 4a ( E / Z = 2:1) and 4b ( E / Z = 2:1) (Scheme ). We also planned to study the cyclizations of silyl ether analogs of complexes 4 , because a silyl protecting group is easier to remove from the anticipated cyclization products when required.…”