Ene-carbonyls

Similarly to alkenes. alkynes also insert. In the reaction of 775 carried out under a CO atmosphere in AcOH, sequential insertions of alkyne, CO. alkene. and CO take place in this order, yielding the keto ester 776[483]. However, the same reaction carried out in THF in the presence of LiCl affords the ketone 777, but not the keto ester[484]. The tricyclic terpenoid hirsutene (779) has been synthesized via the Pd-catalyzed metallo-ene carbonylation reaction of 778 with 85% diastereoselectivity as the key reaction[485], Kainic acid and allo-kainic acid (783) have been synthesized by the intramolecular insertion ol an alkene in 780, followed by carbonylation to give 781 and 782[486],... 

Song and Beak161 have used intramolecular and intermolecular hydrogen-deuterium kinetic isotope effects to investigate the mechanism of the tin tetrachloride catalysed ene-carbonyl enophile addition reaction between diethyloxomalonate and methylenecy-clohexane (equation 105). These ene reactions with carbonyl enophiles can occur by a concerted (equation 106) or a stepwise mechanism (equation 107), where the formation of the intermediate is either fast and reversible and the second step is slow k- > k-i), or where the formation of the intermediate (the k step) is rate-determining. 

On Cr, ene-carbonyl-vinylidene complexes undergo conversion to 2-pyranylidene complexes (Scheme 1.19) [376]. 

Obviously since the products of the geochemical processes contain sulfur and carbon, sources for these elements must be considered but the selection of experimental substrates representing them will await prior chemical process analysis. The result of such an analysis that is relevant to the geosynthesis of compounds from polysulfide aianion and conjugated ene carbonyls will be reviewed briefly later. 

Nonoxidative-recfuctive reactions of sulfur and carbon are illustrated through examples from our ongoing studies of sulfur, in the form of polysulfide, reacting with conjugated ene carbonyls as the carbon source. 

Molecular orbital theory also predicts that a nucleophile of the sulfide type will bond at the carbon terminus of a conjugated ene carbonyl system that is, the nucleophile will bond with the electrophile in the Michael addition mode of reaction (20). Thus, the reaction of polysulfide dianion with an enone represented by a chalcone may proceed initially in such a manner as shown in Scheme 2, which reproduces one of the several pathways... 

The carbon electrophiles studied in my laboratory were chosen because of the preceding theoretical considerations and in view of a need to facilitate the analysis of the anticipated complex product mixtures. Thus, aromatic substituted ene carbonyls were selected because UV-absorbing aromatic units would be incorporated unchanged into products and consequently would assist the detection and isolation of these products. 

An alkaline marine environment high in H2S and HS" is favorable for incorporation of sulfur into organic matter HS" is an aggressive nucleophile. Such conditions also would have been favorable for the formation of polysulfides and elemental sulfur. All of these species, either alone or in combination, are expected to have played a role in the incorporation of sulfur into the vegetable debris that ultimately formed Rasa coal. Many of these species are known to be reactive with hydrocarbons at mild temperatures. Elemental sulfur reacts with hydrocarbons to form organosulfur compounds, including thiophenes at mild temperatures (28,29). Polysulfides react with conjugated ene carbonyls at room temperature to form thiophenes and other sulfur heterocycles (30). ... 

Two other Ni(CO)4 substitutes, Ni(CO)3PPh3 and Ni(COD)2/dppe, prove to be appropriate for the catalysis of tandem metallo-ene/carbonylation reactions of allylic iodides (Scheme 7)399. This process features initial oxidative addition to the alkyl iodide, followed by a metallo-ene reaction with an appropriately substituted double or triple bond, affording an alkyl or vinyl nickel species. This organonickel species may then either alkoxycar-bonylate or carbonylate and undergo a second cyclization on the pendant alkene to give 51, which then alkoxycarbonylates. The choice of nickel catalyst and use of diene versus enyne influences whether mono- or biscyclization predominates (equations 200 and 201). 

Keywords Ene reaction, Hetero-Diels-Alder reaction, Ene cyclization, Desymmetrization, Kinetic resolution. Non-linear effect. Asymmetric activation, Metallo-ene, Carbonyl addition reaction, Aldol-type reaction. Titanium, Aluminum, Magnesium, Palladium, Copper, Lanthanides, Binaphthol, Bisoxazoline, Diphosphine, TADDOL, Schiff base. 

Palladium-catalyzed palladium-ene/carbonylation methodology was also used in an asymmetric diastereoselective total synthesis of (+ )-3-isorauniticine (25) starting from the optically active dienyl carbonate 2371. 

LaLonde R. T., Ferrara L. M. and Hayes M. P. (1987) Low-temperature, polysulfide reactions of conjugated ene carbonyls a reaction model for the geologic origin of S-heterocycles. Org. Geochem. 11, 563-571. 

This led in turn to the idea to also use combinations of different metals (e.g., Co/Rh, Co/Pt, Co/Fe, Co/Mo, Rh/Fe, Rh/Mn, Rh/Re, Rh/W, Rh/Mo) with the aim of creating synergy effects [2]. In the last decade, especially G arland and coworkers accumulated much evidence through spectroscopic measurements and density functional theory (DFT) calculations that in rhodium-catalyzed hydroformylation of non-isomerizable olefins (cyclopentene or 3,3-dimethylbut-l-ene), carbonyl complexes, which are less active in hydroformylation, such as HMn(CO)5 or FIRe(CO)5 [3], can support the reductive elimination of the aldehyde from... 

Heteroaromatic aldehydes such as 3-pyridinecarboxaldehyde react with styrenes to generate 3-chloro-l-(3-pyridyl)-3-phenylpropanols in excellent yields (Scheme 23.67). = However, the reactions are slow compared to the reaction of aryl aldehydes. Aliphatic aldehydes and alkenes do not undergo the reaction, aliphatic aldehydes simply enolize. The reaction of aliphatic alkenes with aryl aldehydes produces mixtures of 1,3-dichloro compounds and ene-carbonyl adducts in very low yield. 

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