Oximes, acid catalyzed alkylation

Formation of 1,2,4-oxadiazines occurs by acid-catalyzed ring expansion of a-aziridino oximes and dioximes, and by 1,3-dipolar cycloaddition of arylcarbonitrile oxides and 2-acyl-2//-azirines (Section 6.14.10). Preparation of l,2,4-oxadiazin-5-ones can be achieved by ring closure of A-carboxymethyl and A-alkoxycarbonylmethyl amidoximes (Section 6.14.9.1.1), by the acid-catalyzed condensation of arylaldehydes with O-alkyl-A-acylhydroxylamines (Section 6.14.9.2.3.1), and by reaction of A-hydroxyureas or amidoximes with a two-carbon fragment such as an a-halo ester or an acyl halide (Section 6.14.9.2.2.1). 

Clerici and Porta reported that phenyl, acetyl and methyl radicals add to the Ca atom of the iminium ion, PhN+Me=CHMe, formed in situ by the titanium-catalyzed condensation of /V-methylanilinc with acetaldehyde to give PhNMeCHMePh, PhNMeCHMeAc, and PhNMeCHMe2 in 80% overall yield.83 Recently, Miyabe and co-workers studied the addition of various alkyl radicals to imine derivatives. Alkyl radicals generated from alkyl iodide and triethylborane were added to imine derivatives such as oxime ethers, hydrazones, and nitrones in an aqueous medium.84 The reaction also proceeds on solid support.85 A-sulfonylimines are also effective under such reaction conditions.86 Indium is also effective as the mediator (Eq. 11.49).87 A tandem radical addition-cyclization reaction of oxime ether and hydrazone was also developed (Eq. 11.50).88 Li and co-workers reported the synthesis of a-amino acid derivatives and amines via the addition of simple alkyl halides to imines and enamides mediated by zinc in water (Eq. 11.51).89 The zinc-mediated radical reaction of the hydrazone bearing a chiral camphorsultam provided the corresponding alkylated products with good diastereoselectivities that can be converted into enantiomerically pure a-amino acids (Eq. 11.52).90... 

Several 1,3,5-triazine mono- and dialdoximes 5 can be prepared by the base-catalyzed condensation of the corresponding methyl-1,3,5-triazines 4 with alkyl nitrites. The formation of either the mono- or the dialdoxime is dependent on the reaction conditons used. Hydrolysis of the oximes to 1,3,5-triazinecarbaldehydes 6 can only be achieved for 4,6-diaryl-l, 3,5-triazine 2-al-doximes. These aldehydes can also be obtained by reaction of 4,6-diaryl-2-methyl-l,3,5-triazi-nes with sodium nitrite in concentrated sulfuric acid.162... 

EtAlCb catalyzes the Friedel-Crafts acylation of alkenes with acid chlorides, the formal [3 + 2] cycloaddition of alkenes with cyclopropane-1,1-dicarboxylates (eq 21), the Friedel-Crafts alkylation of anilines and indoles with ct-aminoacrylate esters, and the formation of allyl sulfoxides from sulfinyl chlorides and alkenes. EtAlCU induces the Beckmann rearrangement of oxime sulfonates. The cationic intermediates can be trapped with enol silyl ethers (eq 22). EtAlC is the preferred catalyst for addition of the cation derived from an a-chloro sulfide to an alkene to give a cation which undergoes a Friedel-Crafts alkylation (eq 23). ... 

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