Unsaturated carbonyl compounds sulfate

Phosphomolybdic acid-Potassium di-chromate-Copper(II) sulfate, 248 Tin(II) trifluoromethanesulfonate, 301 Other unsaturated carbonyl compounds Lead tetraacetate, 155 Pyrylium perchlorate, 263 Zinc-copper couple, 348 a-Substituted-a, p-unsaturated carbonyl compounds... 

The great majority of intramolecular cyclopropanation reactions of unsaturated a-diazo-carbonyl compounds have been achieved with copper catalysts, especially with copper powder or copper bronze, copper(II) sulfate, and bis(acetylacetonato)copper(II). Homogeneous catalysis by bis(salicylaldimato)copper(II) or copper(I) halide/trialkyl phosphite complexes has repeatedly been reported to be superior to heterogeneous catalysis by other copper(I) and cop-per(II) salts, e.g. formation of and 2. ... 

The electrophile E+ can be an alkyl halide or sulfate, an aldehyde to give aldol products, or an a,P-unsatunited ester when conjugate addition is preferred. Examples from simple alkylation show that the alkyl halide can be primary alkyl, allylic 33, and even an a-bromoester or y-bromo-a,P-unsaturated ester 31. The original carbonyl compound that forms the chiral imine with SAMP or RAMP can be an aldehyde 27 or 29, a ketone (symmetrical 32 or blocked on one side 35), or an enone. Only the reagents and products are shown with oxidative [O] or hydrolytic [H20] workup. Notice that SAMP is used for the formation of either enantiomer of 28 by using different starting materials but that RAMP is used to enter the other enantiomeric series from 32. 

In general, the initial formation of the a,p-unsaturated nitrile (72) via Knoevenagel condensation of an activated nitrile (69) with a carbonyl compound (71) mediated by a base ( B) is accepted as a proposed mechanism for the three-component Gewald reaction (G-3CR) (Scheme 12.24). Then, after deprotonation of that intermediate (72), it reacts with elemental sulfur (S ) following an S X mechanism, generating sulfated compound (74), which cyclizes to 75 via an intramolecular nucleophihc attack of the sulfur anion to... 

Chromium compounds increase the activity of platinum catalysts by increasing the electron densities of the active sites. jhe addition of ferrous sulfate, which promotes the hydrogenation of carbonyl groups, and zinc acetate, which inhibits the hydrogenation of double bonds, to platinum gives a catalyst system capable of effecting the selective hydrogenation of an unsaturated aldehyde to an unsaturated alcohoP - (Eqn. 11.12). ... 

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