Pivaloyl chloride, rearrangement with

The reaction of phosphorous acid with pivaloyl chloride in pyridine has been studied three eq. of pivaloyl chloride gave the triacyl phosphite (152). Thiophos-phinltes or monothiophosphites (153) rearrange spontaneously to the thiophosphoryl isomer (154) in the presence of oxygen. The rearrangement was inhibited by the addition of radical inhibitors. Irradiation of a mixture of naphthalene or phenanthrene and trialkyl phosphites in the presence of 1,3-dicyanobenzene gave several isomeric monophosphonates. ... 

Silylphosphines, e.g. (100), react with pivaloyl chloride to form the unstable acyl-phosphines (101), which rearrange to form the enol species (102) these appear to involve P=C p -p bonding. - ... 

Acyl phosphines are readily formed from phosphinosilanes but, with phosgene and oxalyl chloride, decarbonylation and rearrangement results with formation of intermediate methylenephosphanes which cyclize giving 18 and 19 (equations 33 and 34 and Scheme 10)37. With the more hindered pivaloyl chloride, the methylenephosphane... 

The acylium ion is particularly stable and generally does not easily undergo rearrangement reactions unlike F-C alkylations. If the acylium ion VIII can produce an especially stable carbocation and reacted with an arene of modest reactivity, side products can form via a competing F-C alkylation pathway. An example of such is the competing F-C acylation-alkylation pathways in the attempted pivaloylation of neat benzene versus anisole. The reaction of benzene with pivaloyl chloride in the presence of AICI3 catalyst produces ter/-butylbenzene as the major product, whereas the reaction of... 

A stereochemical control of the Ugi reaction can be effected with carbohydrates as chiral templates (e.g. tetrakis(O-pivaloyl)galactosylamine), which gives rise to easily separable amides. From these a variety of non-natural amino acids can be derived after acidic hydrolysis. The Passerini reaction, related to the Ugi rearrangement, gives a-hydroxyamides. A modification of this reaction using titanium tetrachloride gives a-branched amides in high yields via C-metalated imidoyl chlorides (equation 38). 

As expected, the reaction products after decompression and quenching with hydrochloric acid and ice water were pivalic acid, terr-butyl isobutenyl ketone (in the absence of a hydride donor, this unsaturated ketone replaced the saturated congener, and no isopropyl methyl ketone by rearrangement of the pivaloyl cation could result). An unexpected crystalline material also appeared in small yield when the aqueous solution was saturated with sodium chloride for facilitating the extraction of organic reaction products. This proved to be a pyrylium salt, as will be shown below. 

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