A mild oxidation of aldehydes to α,β-unsaturated aldehydes

Reactions of unactivated olefins with Vilsmeier reagents

“…a,P-Unsaturated aldehydes are important in synthetic organic chemistry (18) and previous preparations include: (i) from ketones by one-carbon homologation procedures (19,20); (ii) from methyl vinyl ethers by photooxidation (18); (iii) from aldehydes via organolithium derivatives (20,(22)(23)(24) or by oxidation via a-chloroaldimines (1 8); (iv) from a-bromoaldehydes via N, N-dimethylhydrazones (25) or piperidine enarnines (26); (v) from a-lithiated allenic sulfides (27); and (vi) a single example (for l-cyclohexenecarboxaldehyde) from a nitromethylolefin (28).…”

Benzeneselenenyl Reagents in Organic Synthesis

“…Most commonly, electrophilic benzeneselenenyl transfer reagents are used in the a-benzeneselenenylation of carbonyl compounds to form a-phenylseleno car-bony1 compounds 41 (scheme 6). Almost all methods require enol derivatives 40 such as enol ethers (YR3 = OR) [70, 7 11, silyl enol ethers (YR3 = OSiMe3) [72], enol acetates (YR3 = 02CCH3) [14,73], enamines (YR3 = NR,) [74], or lithium enolates (YR3 = OLi) [ [92] in the presence of tributylphosphine (scheme 7, 48 3 49). Another direct conversion of alcohols to the corresponding phenyl selenides utilizes benzeneselenol (4) in the presence of zinc chloride [93].…”

“…Common reagents for the oxidation of phenyl selenides to phenyl selenoxides are sodium periodate (cf. 105 + 106) [14,16,74,75,1601, peracids (meta-chloro perbenzoic acid or peracetic acid) [14,16,29,74,1371, ozone [7, 14, 1601, or hydrogen peroxide [51,89, 137, 160, 1611 (scheme 18).…”

Cesium Carbonate-Catalyzed α-Phenylchalcogenation of Carbonyl Compounds with Diphenyl Dichalcogenide

“…α - Phenylselenocarbonyl compounds are useful synthetic intermediates in organic synthesis [ 1 , 2 , 3 , 4 , 5 ] and much effort is being devoted to accomplish the synthesis of these compounds. There are many reports on the preparation of α - phenylselenocarbonyl compounds: (i) electrophilic reaction with PhSeX, PhSeX 3 , PhSeO 2 CCF 3 or phenylselenium cation (PhSe + ), which was generated in situ from the treatment of diphenyl diselenide with SeO 2 , benzeneseleninic anhydride, chloramine-T, or Et 4 NBr or MgBr 2 under electrolysis [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]; (ii) nucleophilic displacement of α-halocarbonyl compounds with sodium and lithium phenylselenolate [ 22 ]; (iii) insertion of carbene into carbon-selenium bond of selenol esters [ 23 ]; (iv) palladium-catalyzed coupling of phenyl tributylstannyl selenide and α-halocarbonyl compounds [ 24 ] and (v) organocatalyst-catalyzed reaction of carbonyl compounds with N -(phenylseleno)phthalimide [ 25 , 26 , 27 , 28 ]. However, many of these synthetic methods suffer from the the problems of handling the selenium reagents used as selenium sources because of their instability towards air and moisture, acidic or basic reaction conditions, and the use of stoichiometric amounts of acid or base.…”