Magnesium alkylidene carbenoids alkenylation

A very interesting direct alkenylation of aryiamines at the ortho-position by the reaction of magnesium alkylidene carbenoids with A-lithio aryiamines to give 162 was reported by Satoh and coworkers (equation 40) . Magnesium alkylidene carbenoid 157, derived... 

Very interesting results were obtained from the reaction of magnesium alkylidene carbenoids with mefa-substituted arylamines (Table 8) . The reaction of magnesium alkylidene carbenoids 157 and 161 with three mefa-substituted anilines was carried out and the results are summarized in Table 8. The reaction of 157 with meta-anisidine gave two products 163 and 164 (in a 30 13 ratio) in 43% yield. The main product was found to have the alkenyl group at the more hindered position (163). As shown in the Table, all the other meto-substituted aniline derivatives also gave the more hindered alkenylated compounds as the main product in variable ratio. 

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

The direct alkenylation of arylamines at the ortho -position with magnesium alkylidene carbenoids has been investigated using both theoretical and experimental approaches." In some cases, the reaction has proceeded in a highly stereospecific manner at the carbon bearing the chlorine and the sulflnyl group. 

Treatment of magnesium alkylidene carbenoids, which were generated from 1-chlorovinyl /)-tolyl sulfoxide 161 with isopropylmagnesium chloride at —78°C in toluene, with AT-lithioindazole 162 (or pyrazole) gave N-alkenylated indazole 163 in moderate yield (Scheme 5) <2005TL4855>. Reaction of lithiopyrazole gave the N-alkenylated pyrazole but in a lower yield. 

---