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Ethynylmagnesium chloride

In the direct synthesis of aryl terminal alkynes via Pd-catalyzed cross-coupling of aryl halides with ethynylmetals, formation of diarylethynes is one of the potential side reactions. Indeed, the Kumada coupling of 2-iodo-5-methylthiophene (29) with ethynylmagnesium chloride gave the desired 2-ethynyl-5-methylthiophene (30) in only 35% yield, along with 24% of bis(5-methyl-2-thienyl)ethyne (31) [29], The high propensity for H-Mg exchange reaction to occur was blamed for the diarylethyne formation. [Pg.238]

Trimethylsilylacetylene is prepared by sllylation of ethynylmagnesium chloride as described in the accompanying procedure in Organic Syntheses. It is also commercially available from the Aldrich Chemical Company, Inc. [Pg.28]

The temperature reaches 15°C after 0.5 hr, and 20°C after 0.8 hr. Ethynylmagnesium halides can rapidly disproportionate to bis(chloromagnesium)-acetylene and acetylene at higher temperatures. It is important to maintain the reaction mixture at or below 20°C and to have an excess of acetylene in order to prevent formation of the bis(magnesium chloride). The checkers found that the ethynylmagnesium chloride can be formed at 10-15°C, thus minimizing the problem. [Pg.33]

It is important that the addition be done fairly rapidly. The checkers found that slow addition (2 hr at 20°C) resulted in significant disproportionation of the ethynylmagnesium chloride. [Pg.33]

Information in this area is particularly sparse. Even when reverse addition methods are employed, low yields of dialkyl ethynylphosphonates are obtained for a dialkyl phos-phorochloridate and ethynylmagnesium bromide (reaction 35 R = RO, X = Cl). The use of a dialkyl phosphorofluoridate (230) (R = RO, X = F) with the same organometallic reagent obviates the need for reverse addition, and the overall yields are then improved". One more recently recorded example consists in the interaction of ethynylmagnesium chloride with methyl methylphosphonochloridate (230) (R = R = Me X = Cl) to give methyl ethynylmethylphosphinate ... [Pg.99]

Mg acetylides are easily prepared and used for coupling. A good preparative method of 1-alkynes is the coupling of commercially available ethynylmagnesium chloride (122) or ethynylzinc chloride (123) as acetylene surrogates with aryl or alkenyl halides. Their couplings with halides directly afford the 1-alkynes 124. No deprotection is necessary [60]. [Pg.220]


See other pages where Ethynylmagnesium chloride is mentioned: [Pg.238]    [Pg.130]    [Pg.864]    [Pg.32]    [Pg.34]    [Pg.180]    [Pg.42]    [Pg.187]    [Pg.63]    [Pg.64]    [Pg.66]    [Pg.650]    [Pg.340]    [Pg.340]    [Pg.1510]    [Pg.13]    [Pg.566]   
See also in sourсe #XX -- [ Pg.340 ]




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Ethynylmagnesium

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