Alkenylations pivalic acid

Chelation-assisted alkenylation of the ortho-C-H bond of aryl carbamates Ar-OCONEt2 with alkynes R C=CR, catalysed by [(p-cymene)RuCl2]2 in the presence of AgSbFg and pivalic acid at 100 °C over <24 h, has been shown to proceed... 

Direct Alkenylation of Heteroarenes. Pivalic acid enhanced both yield and selectivity for the C2-selective olefination of pyridine. Other acid additives performed inferiorly to pivalic acid 2.5 equiv of PivOH was the ideal amount to maximize product yield. Silver(I) acetate functioned as a terminal oxidant and also positively influenced yield and selectivity. Only small amounts of C3 product were detected. 

Triazole iV-oxides could be site-selectively C5-alkenylated under oxidative conditions using silver(I) carbonate as an oxidant and pivalic acid as an additive (eq 7). ... 

Various functional alkenes were similarly synthesized with high regio and E-stereoselective manner via [RuCl2(p-cymene)]2/AgSbF6 catalysed hydroarylation of phenyl or ester substituted alkynes with aromatic carbamates. The addition of 5 equiv. of pivalic acid improves the reaction in 1,4-dioxane. The alkenyl ester is converted into carboxylic acid by using 2 equiv. of LiOH, whereas phenol derivatives were deprotected by addition of 10 equiv. of LiOH [(Eq. 82)] [166]. 

Atyl carbo lates and alkenyl acetates were also catalytically coupled with arylboroxines using NiCl2(PCy3)2 (Scheme 14.22). It was found that water can promote this transformation. The optimal amount of water is 0.88 equivalents (based on the acetate) for the atyl carbojgrlates and 1.0 equivalents for the alkenyl acetates.However, NiCl2(PCy3)2-catalysed coupling of aryl pivalates with aryl boronic acids does not require a water additive. ... 

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