Cyclobutanones and Cyclobutenones in Nature and in Synthesis [New Synthetic Methods(71)]

Carbon monoxide (CO) is in principle an excellent resource from which to produce industrial hydrocarbon feedstocks as alternatives to crude oil; however, CO has proven remarkably resistant to selective homologation, and the few complexes that can effect this transformation cannot be recycled because liberation of the homologated product destroys the complexes or they are substitutionally inert. Here, we show that under mild conditions a simple triamidoamine uranium(III) complex can reductively homologate CO and be recycled for reuse. Following treatment with organosilyl halides, bis(organosiloxy)acetylenes, which readily convert to furanones, are produced, and this was confirmed by the use of isotopically 13C-labeled CO. The precursor to the triamido uranium(III) complex is formed concomitantly. These findings establish that, under appropriate conditions, uranium(III) can mediate a complete synthetic cycle for the homologation of CO to higher derivatives. This work may prove useful in spurring wider efforts in CO homologation, and the simplicity of this system suggests that catalytic CO functionalization may soon be within reach.

https://www.pnas.org/content/pnas/109/24/9265.full.pdf

Homologation and functionalization of carbon monoxide by a recyclable uranium complex.

Publisher Summary Metal carbonyls, which were among the earliest discovered organometallic compounds, continue to play a central role in organometallic chemistry. Carbonyl basicity is found for C-bridging CO ligands in metal–metal bonded compounds, CO ligands in anionic metal carbonyls, or CO ligands in donor-substituted metal carbonyls. The interaction of protons with mononuclear metal carbonyls readily occurs at the metal center rather than the CO oxygen; no stable or transient MCO–H species appear to have been observed. The chemical and structural characterization of molecular compounds containing π–CO is of great interest, because the π–CO is implicated as a precursor to the cleavage of CO on metal surfaces, such as those employed in Fischer–Tropsch catalysis. In view of these large physical changes, it perhaps is not surprising that C and O bonding also engenders large changes in CO reactivity. Carbon monoxide insertion into a metal–alkyl bond is a fundamental reaction in organometallic chemistry as well as an important step in the commercial production of oxygen-containing organics, such as aldehydes and acetic acid.

C- and O-Bonded Metal Carbonyls: Formation, Structures, and Reactions

7.3 – Transition Metal Alkyne Complexes: Transition Metal-catalyzed Cyclotrimerization

Organocobalt compounds in organic synthesis have three characteristic reactions. The first occurs because cobalt has a high affinity to carbon–carbon π-bonds or carbon–nitrogen π-bonds. The second occurs because cobalt has a high affinity to carbonyl groups. The third is due to cobalt easily tending to form square-planar bipyramidal six-coordination structures with four nitrogen atoms or two nitrogen atoms and two oxygen atoms at the square-planar position, and to bond with one or two carbon atoms at the axial position. The first characteristic reactions are the representative reactions of organocobalt compounds with a mutually bridged bond between the two π-bonds of acetylene and the cobalt–cobalt bond of hexacarbonyldicobalt. These are reactions with a Co2(CO)6 protecting group to reactive acetylene bond, the Nicholas reactions, the Pauson–Khand reactions ([2 + 2 + 1] cyclizations), [2 + 2 + 2] cyclizations, etc. These reactions are applied for the syntheses of many kinds of pharmaceutically useful compounds. The second reactions are carbonylations that have been used or developed as industrial processes such as hydroformylation for the manufacture of isononylaldehyde, and carbonylation for the production of phenylacetic acid from benzyl chloride. The third reactions are those reactions with the B12-type catalysts, and they have recently been used in organic syntheses and are utilized as catalysts for stereoselective syntheses. These reactions have been used as new applications for organic syntheses. Copyright © 2007 John Wiley & Sons, Ltd.

Three characteristic reactions of organocobalt compounds in organic synthesis

Synthetic applications of di-tert-butoxyethyne, II: New syntheses of squaric, semisquaric and croconic acids

Diisopropoxy- and di-tert-butoxyethyne : Stable acetylene diethers

The electrochemical demetallation of (η-tetra-t-butoxycyclopentadienone)(ηcyclopentadieny)cobalt, readily available from di-t-butoxyethyne leads to tetra-t-butoxyclopentadienone which can be converted into hydrocroconic acid by trifluoroacetic acid hydrolysis and then croconic acid by oxidation in basic medium.

Synthesis of croconic and hydrocroconic acids from di-t-butoxyethyne. Electrochemical demetallation of a cyclopentadienyl organocobalt complex

Dialkoxyacetylenes: di-tert-butoxyethyne, a valuable synthetic intermediate 



intermediate: trans-2,3-dichloro-1,4-dioxane




intermediate: trans-2-tert-butoxy-3-hydroxy-1,4-dioxane




intermediate: trans-2,3-di-tert-butoxy-1,4-dioxane




intermediate: cis- and trans-2,3-di-tert-butoxy-1,4-dioxane




intermediate: 1,2-di-tert-butoxy-1,2-dichloroethane




intermediate: (E)-1,2-di-tert-butoxy-1-chloroethene




product: di-tert-butoxyethyne




byproduct: 0.1–0.5 g of cis-2,3,7,10-tetraoxabicyclo[4.4.0]decane




byproduct: (Z)-1,2-di-tert-butoxy-1-chloroethane




byproduct: 1,2,3-tri-tert-butoxy-3-cyano-1-propene




byproduct: 1,2,3-tri-tert-butoxy-1-cyano-1-propene





Keywords:

acetal (and thioacetal) formation;
elimination, dehydrohalogenation;
elimination, dehydrohalogenation;
halogenation, chlorination;
halogenation, chlorination;
replacement reactions, ether by halogen;
sodium amide, preparation of;
chlorine;
diazo compounds;
sodium hydride, disposal

Anna Bou

Papers

Synthetic applications of di-tert-butoxyethyne, II: New syntheses of squaric, semisquaric and croconic acids

Diisopropoxy- and di-tert-butoxyethyne : Stable acetylene diethers

Synthesis of croconic and hydrocroconic acids from di-t-butoxyethyne. Electrochemical demetallation of a cyclopentadienyl organocobalt complex

Dialkoxyacetylenes: di‐tert‐butoxyethyne, A Valuable Synthetic Intermediate