Magnesium carbenoids synthesis

Stereoselective preparation of functionalized unsaturated lactones and esters via functionalized magnesium carbenoids. Synthesis 2003, 1797-1802. 

TABLE 2. Synthesis of a-amino esters from magnesium carbenoids by the reaction with A-hthio A-substituted arylamines followed by ethyl chloroformate... 

Pioneered by Villieras, the Hal/Mg exchange reaction has been applied as a general method for the synthesis of magnesium-containing carbenoids. The treatment of CHBrs (24) with /-PrMgCl at -78 °C leads to the magnesium carbenoid 25, which can be reacted with TMSCl affording dibromomethyltrimethylsilane (26) in excellent 90% yield (Scheme 2-17). ... 

Scheme4,56 Pyrimidine synthesis using magnesium carbenoids.

Synthesis of allenes by alkenylation of magnesium aikyiidene carbenoids with a-suifonyi iithium carbanions... 

TABLE 7. Synthesis of ortfto-alkenylated arylamines (162) by the reaction of the magnesium alkyh-dene carbenoids with A-hthio arylamines... 

TABLE 8. Synthesis of ort/to-alkenylated arylamines 163 and 164 by reaction of magnesium alkylidene carbenoids with meta-substituted A-hthio arylamines... 

Magnesium alkyUdene carbenoids were found to be reactive with different nucleophiles to give new alkenyhnagnesium compounds which could be trapped with electrophiles. As a whole, novel methods for the synthesis of tri- or tetrasubstimted olefins from the 1-chlorovinyl p-tolyl sulfoxides in a one-pot reaction are realized. 

TABLE 12. Synthesis of enyne 183 from magnesium alkylidene carbenoids 134a with lithium acetylides and electrophiles... 

TABLE 13. Synthesis of vinyl sulfides (185) by the reaction of magnesium alkyU-dene carbenoids with lithium thiolates... 

Satoh and coworkers further investigated this reaction and found that, in some cases, magnesium /3-oxido carbenoids gave better results. Trapping of the enolate intermediates with several electrophiles was successfully carried out and a new method for the synthesis of one-carbon expanded cyclic a,a-disubstituted ketones from lower cyclic ketones was realized. An example using 1,4-cyclohexanedione mono ethylene ketal (195) as a representative cyclic ketone is shown in Table 15. ... 

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