Selective mono- and polymethylene homologations of copper reagents using (iodomethyl)zinc iodide

Sidduri, Achyutharao; Rozema, Michael J.; Knöchel, Paul

doi:10.1021/jo00062a010

Cited by 119 publications

(33 citation statements)

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“…[14] This process has been utilized successfully in the alkylation of α-haloalkylmetals (e.g., M ϭ Mg, [15] Zn, [16] B, [17] or Cu [18] ) and allows the facile introduction of an alkyl group to the organometallic reagents. This process enables complex metallic reagents to be prepared from relatively simple and easily accessible organometallic species.…”

Section: Methodsmentioning

confidence: 99%

Transition Metal‐Catalyzed Carbon−Carbon Bond Formation with Grignard Reagents − Novel Reactions with a Classic Reagent

2004

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Keywords: Chromium / Cobalt / Grignard reagent / Iron / Manganese Organomagnesium compounds are among the most useful organometallic reagents in organic synthesis. Besides their classical nucleophilic reactions to carbonyl compounds, Grignard reagents gain versatile reactivity when combined with various transition metal salts. In this article, we review mainly our own studies on manganese-, iron-, chromium-,

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Section: Methodsmentioning

confidence: 99%

Transition Metal‐Catalyzed Carbon−Carbon Bond Formation with Grignard Reagents − Novel Reactions with a Classic Reagent

2004

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“…(17), 83 (15), 69 (51), 55 (100). 30 Prepared according to typical procedure A. Methyl 4-Methenyloctanoate (22c) 31 Prepared according to typical procedure A.…”

Section: Dec-5-ene (20) 29mentioning

confidence: 99%

Iron-Catalyzed Alkenylation of Grignard Reagents by Enol Phosphates

Cahiez¹,

Gager²,

Habiak³

2008

Synthesis

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Stereoselective preparation of trisubstituted olefins can be easily performed from an Z/E-mixture of enol phosphates by reacting only the E-isomer with a Grignard reagent in the presence of Fe(acac) 3 . This procedure combines a kinetic differentiation and a stereoselective reaction. The coupling is very chemoselective in the presence of an alkyl chloride, an ester, a ketone or a nitrile.The first example of iron-catalyzed cross-coupling reactions between a Grignard reagent and a vinylic halide was described by Kharasch in 1945. 1 Kochi, in 1971, studied the mechanism of the coupling between alkylmagnesium reagents and vinyl or propenyl bromide. 2 Unfortunately, from a preparative point of view, the reaction was not very attractive since its scope was limited to reactive vinylic halides such as propenyl bromide or b-bromostyrene. 3 Moreover, as a rule, a large excess of these substrates (3 to 9 equivalents) had to be used in order to obtain satisfactory yields. Twenty years later, the chemistry of iron-catalyzed cross-coupling reactions was still in its infancy since no general preparative procedure had been described. At this time, we were convinced that iron salts such as FeCl 3 , and Fe(acac) 3 were a valuable alternative to the palladium and nickel complexes commonly used as catalysts for many coupling procedures since they were cheaper and much more environmentally sound. Thus, we have reinvestigated the iron-catalyzed coupling of Grignard reagents with alkenyl halides and have finally discovered that, in the presence of N-methyl-2-pyrrolidinone (NMP) as an additive, the reaction occurs almost instantaneously to give excellent yields, even from the less reactive alkenyl chlorides. 4,5 In addition, the reaction is highly chemo-and stereoselective (Scheme 1).The use of NMP is a major advance in the field of ironcatalyzed cross-coupling reactions. Thus, our conditions have since been used by Fürstner to couple alkylmagnesium reagents with aryl chlorides. 6 In the last few years, iron-catalyzed reactions have received considerable interest as indicated by the increasing number of reports from us 5c,7 and others. 6,8 The alkenylation reaction previously described is very efficient and offers many economical and environmental advantages. However, the starting alkenyl halides are not always easy to prepare. To circumvent this problem in the case of the palladium-and nickel-catalyzed reactions, a classical alternative is to replace alkenyl bromides or iodides by the corresponding enol triflates, which often react similarly. 9 However, these substrates are not very convenient for preparative chemistry. Indeed, although triflates are very useful on a laboratory scale, they do not constitute a valuable industrial alternative to alkenyl halides since they are expensive and relatively difficult to handle and purify on a large scale. From this point of view, enol phosphates are much more attractive since they are less expensive. Moreover, they are stable enough to be prepared, stored and isolated without problem. Thus,...

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“…The stereoselectivity of the reaction results from a Zimmerman — Traxler transition state in which the substituent of the incoming aldehyde occupies a pseudo equatorial position (Scheme 12, path B). 4c In the third system, we increased the 1,3-steric diaxial interaction by adding bulky ligands on the zinc center. Indeed, when vinyl iodide 12a was in-situ transformed into the vinyl copper species followed by the addition of phosphate-based carbenoid 30 and aromatic aldehyde, the expected adduct was obtained in moderate yield but with a low diastereomeric ratio (Scheme 12, path C).…”

Section: Introductionmentioning

confidence: 99%

Axial Preferences in Allylation Reactions via the Zimmerman–Traxler Transition State

et al. 2013

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CONSPECTUS The reaction of substituted allylmetal on prostereogenic carbonyl compound can give rise to up to two racemic diastereomers (syn and anti). Classically, when anti selectivity was observed from pure E-isomers while the Z-isomers exhibit syn-selectivity, the empirical Zimmerman – Traxler model is used. In this model, chair-like transition states are predicted to dominate over boat-like arrangements and the incoming aldehyde alkyl (aryl) residue occupies a pseudo-equatorial rather than a pseudo-axial position to avoid potential 1,3-diaxial steric interactions. However, the stereochemical outcome of the reaction of γ,γ-disubstituted allylzinc species with carbonyl compounds reaction may be completely different as two gauche interactions are generated. Would the two gauche interactions present in the transition state where the aldehyde substituent occupies a pseudo-equatorial position be preferred to a transition state in which the same substituent of the aldehyde occupies a pseudoaxial position? In this study, we could show that reaction of γ,γ-disubstituted allylzinc species with carbonyl compounds proceeds through a chair-like transition state and the substituent of the incoming aldehyde residue prefers to occupy a pseudo-axial rather than into a pseudo-equatorial position to avoid these two gauche interactions. Our experimental results were supported by theoretical calculations on model systems. This new stereochemical outcome has been extended to the formation of α-alkoxyallylation of aldehydes through the formation of the rather uncommon (E)-γ,γ-disubstituted alkoxyallylzinc species. This method could also be used to transform aromatic ketones as well as α-alkoxyaldehydes and ketone into functionalized adducts in which three new carbon-carbon bonds and two to three stereogenic centers, including an all-carbon quaternary stereocenter, were created in an acyclic systems in a single-pot operation from simple alkynes. Increasing the size of substituents on the zinc atom decreases the diastereoselectivity since 1,3-diaxial interactions are now produced with the axial substituent.

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Selective mono- and polymethylene homologations of copper reagents using (iodomethyl)zinc iodide

Cited by 119 publications

References 0 publications

Transition Metal‐Catalyzed Carbon−Carbon Bond Formation with Grignard Reagents − Novel Reactions with a Classic Reagent

Transition Metal‐Catalyzed Carbon−Carbon Bond Formation with Grignard Reagents − Novel Reactions with a Classic Reagent

Iron-Catalyzed Alkenylation of Grignard Reagents by Enol Phosphates

Axial Preferences in Allylation Reactions via the Zimmerman–Traxler Transition State

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