Collman carbonylation reaction

Cycloalkanones. M6rour etaO have reported that Collman s reagent converts a y-ethylenic bromide or tosylate into a cyclohexanone and a -allenic bromide into a cyclopentenone in moderate yield. This carbonylation reaction represents a special O... 

Applications of carbonylate reactions in organic synthesis are numerous. Particularly noteworthy are schemes involving tetracaibonylferrate( -11) (referred to as Collman s reagent), which can be isolated as a sodium salt, Na2Fe(CO)4-1.5 dioxane, and is commercially available. The highly nucleophilic [Fe(CO)4]2 reacts readily with alkyl halides to yield alkyl iron carbonylates ... 

The phenomenon of metal transport via the creation of volatile metal carbonyls is familiar to workers using carbon monoxide as a reactant. It is often found that carbon monoxide is contaminated with iron pentacarbonyl, formed by interactions between carbon monoxide and the walls of a steel container. Thus, it is common practice to place a hot trap between the source of the CO and the reaction vessel. Iron carbonyl decomposes in the hot trap and never reaches the catalyst that it would otherwise contaminate or poison. Transport of a number of transition metals via volatile metal carbonyls is common. For example, Collman et al. (73) found that rhodium from rhodium particles supported on either a polymeric support or on alumina could be volatilized to form rhodium carbonyls in flowing CO. 

The most commercially important metal carbonyl anion, [Fe(CO)4]2, contained in Collman s reagent (shown below), can be prepared from the following reaction in dioxane solvent.14... 

A.iii. Sodium Tetracarbonyl Ferrate. An extremely useful organoiron reagent is sodium tetra-carbonyl ferrate [Na2Fe(CO)4], usually prepared by reduction of iron pentacarbonyl. The synthetic utility of this reagent lies in its ability to react with alkyl halides in a stepwise manner, including the reaction with two different alkyl halides, as reported independently by Cooke and by Collman and co-workers. - When sodium tetracarbonyl ferrate reacted with 1-bromooctane, a trigonal bipyramidal complex (715) was formed... 

Alkylation of the enolate of (138) with methallyliodide gave the product (149) whose stereochemistry was assigned on the basis of equilibration experiment. It was converted to the dione (150) by oxidation with osmium tetrooxide and sodiumperiodate. The aldol cyclization of (150) effected with sodium hydride and trace of t-amyl alcohol in refluxing benzene afforded the enone (151) in 88% yield. Normal protic conditions (sodium hydroxide, ethanol) were not effective in this transformation. All attempts for its conversion to aphidicolin (148) by intermolecular additions proved fruitless and therefore were turned to intramolecular methods. Molecular models show clearly that the top face of the carbonyl group is less hindered to nucleophilic attack than is the bottom face. Thus the reduction of (151) with lithium aluminium hydride afforded the alcohol (152) whose vinyl ether (153) was subjected to pyrolysis for 2 hr at 360 C in toluene solution containing a small amount of sodium t-pentoxide to obtain the aldehyde (154) in 69% yield. Reduction and then tosylation afforded the alcohol (155) and tosylate (156) respectively. Treatment of this tosylate with Collman s reagent [67] (a reaction that failed in the model system) afforded the already reported ketoacetonide (145) whose conversion to aphidicolin (148) has been described in "Fig (12)". 

Collman has investigated the formation of metal-metal bonded oligomers using hydrido-germanium- and -tin-metal carbonyl derivatives, which were first synthesized by the reduction of the corresponding tin and germanium chlorides with Bu AlH in hexane. The results jof coupling reactions are summarized in Scheme 25. ... 

Phosphorus, the most important ligand element, can be introduced via many routes. For example, (1) halogenated polystyrene is reacted with butyllithium followed by reaction with ClPPh2 (Evans et al., 1974) and (2) the resin is treated with PPh2Li (Nonaka et al., 1974) to produce the same functionalized polymer. The supports thus produced have been used to immobilize carbonyls such as Ni(CO)4 (Nonaka et al., 1974), (PPh3)3RhH(CO) (Pittman and Felis, 1974), and Rh6(CO)ig (Collman et al., 1972). 

Complexation of alkenes to iron carbonyl fragments increases the electrophilicity of the alkene, owing to the electron-withdrawing ability of the carbonyl ligands. The anion of dimethyl malonate will attack the iron tetracarbonyl complex of methyl acrylate 6.295 (Scheme 6.113). " The resulting anion 6.296 is obviously related to the intermediates involved in the reactions of Collman s reagent (Section 4.5.1). Thus, carbonylation and addition of an alkyl halide results in acylation. 

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