Oxidation open-chain alkyl

The efficiency of oxidation of open-chain alkyl, cycloalkyl, and unsaturated alcohols in acetonitrile by 9-phenylxanthylium ion (PhXn+) was dependent on the alcohol stmc-tures. Structure-reactivity relationship was discussed with relation to formation of a carbocationic transition state (C +-OH). Kinetic isotope effects determined at a-D, p-D3, and OD positions for the reaction of 1-phenylethanol suggested a hydride-proton sequential transfer mechanism that involved a rate-limiting formation of the a-hydroxy carbocation intermediate. Unhindered secondary alkyl alcohols were selectively oxidized in the presence of primary and hindered secondary alkyl alcohols. Strained C(7)-C(ll) cycloalkyl alcohols reacted faster than cyclohexyl alcohol, whereas the strained C(5) and C(12) alcohols reacted slower. Aromatic alcohols were oxidized efficiently and selectively in the presence of aliphatic alcohols of comparable steric requirements. ... 

Electrogenerated monovalent Co complexes of the well-known open chain N202 Schiff base ligands salen (8), salphen (9), and their substituted derivatives undergo oxidative additions with alkyl halides. Reactions of the complex with substrates within the series RBr (R = Pr, Bu, t-Bu) proceed at different rates. The reaction occurs by an inner-sphere alkyl-bridged electron transfer, with a Co1- R+- X-transition state, which is sensitive to distortions of the complex in different configurations.124... 

The preparation of novel phase transfer catalysts and their application in solving synthetic problems are well documented(l). Compounds such as quaternary ammonium and phosphonium salts, phosphoramides, crown ethers, cryptands, and open-chain polyethers promote a variety of anionic reactions. These include alkylations(2), carbene reactions (3), ylide reactions(4), epoxidations(S), polymerizations(6), reductions(7), oxidations(8), eliminations(9), and displacement reactions(10) to name only a few. The unique activity of a particular catalyst rests in its ability to transport the ion across a phase boundary. This boundary is normally one which separates two immiscible liquids in a biphasic liquid-liquid reaction system. 

Depending on the alkene cation radical nature, open-chain oxygenation and epoxida-tion take place as well as the formation of other trivial ozonolysis products. Alkylaromatic compounds are also oxidized by ozone via the ion radical mechanism. Ethylbenzene, for example, undergoes ozone attack on the ring (80%) and on the alkyl group (20%). According to kinetic studies, the ozone consumption obeys the chain law (Galstyan et al. 2001). 

Monocyclic Phosphoranide Anion. The intramolecular oxidative addition of hydroxyalkyl phosphites, which gives P-H phosphoranes, is well known (10). Some P-H phosphoranes are so stable that the open-chain P(III) tautomers cannot be detected spectroscopically or even by attempted H2O2 oxidation (8). Thus, it is surprising to find no evidence for an equilibrium between phosphine alcohol 1 and its closed-ring tautomer phosphorane 2. Phosphine 1 is quaternized by alkyl halides giving phosphonium halides such as 3. These in turn are converted to alkoxyphosphor-anes, such as 4 by NaH (Scheme I). 

Alkyl-2-(fV-cyanoimino)thiazolidine 1-oxides 684 undergo a ring-enlargement process in the presence of trifluoro-acetic anhydride to afford 5,6-dihydro-2//-l-thia-2,4-diazin-3(4//)-ones 685 (Scheme 297). Initial reaction of 684 with the anhydride leads to open-chain imidate 686, intramolecular displacement of trifluoroacetate gives 4//-l-thia-2,4-diazine 687, which finally hydrolyzes to the isolated product 685 (Scheme 297) <1997SL316, CHEC-III(9.05.10)334>. 

The hydrolysis (or alcoholysis) of furans involves nucleophilic addition of water (or an alcohol) to an initially formed cation, giving rise to open-chain 1,4-dicarbonyl-compounds or derivatives thereof. This is in effect the reverse of one of the general methods for the construction of furan rings (18.13.1.1). Suc-cindialdehyde cannot be obtained from furan itself, presumably because this dialdehyde is too reactive under conditions for hydrolysis, but some alkyl-furans can be converted into 1,4-dicarbonyl products quite efficiently, and this can be viewed as a good method for their synthesis, and of cyclopentenones derived from them. ° Other routes from furans to 1,4-dicarbonyl compounds are the hydrolysis of 2,5-dialkoxy-tetrahydro-furans (18.1.1.4) and by various oxidative procedures (18.2). 

Phthalazine-l(2 T)-thione reacts in a similar manner with alkenes by [2 + 2] addition, but the intermediate diradical either cyclizes on to the /jen-position to give, after oxidation, the fused tricyclic system (105), or undergoes hydrogen transfer to give open chain sulfides (Scheme 68). The formation of the fused products is favoured by stabilization of the terminal alkyl radical by geminal methyl substitution <90CPB1205>. 

Acetoxy-3,5-dimethoxyphenyl)-5,7-diacetyl-3-acetoxyflav-3-ene has been synthesised from the quinonemethide shown by addition to a benzene/dimethyl formamide (25 1) solution of phloroglucinol followed by reaction for 2 mins, in the presence of a catalytic quantity of 4-toiuenesulphonic acid to give initially the open chain C-alkylated intermediate in 48% yield. This was stirred for 48 hours at ambient temperature in benzene/acetone containing silver oxide and was then acetylated with acetic anhydride/pyridine (ref. 10). 

Since then researchers in the field of nitrone cycloaddition seem to have more or less tacitly assumed that secondary interactions play an important role in determining endo/exo selectivity also in the case of N-alkyl and N-arylnitrone cycloaddi-tions.2 However, our experimental endo/exo selectivity studies " for the reactions of cyclic and open-chain nitrones with Z-disubstituted dipolarophiles revealed a clear-cut dominance (77% in benzene) of the endo mode only in one case the reaction of 1-pyrroline-l-oxide with maleonitrile, a reaction where the steric effects... 

---