Oxidation, of terminal olefins with

ALDEHYDES BY OXIDATION OF TERMINAL OLEFINS WITH CHROMYL CHLORIDE 2,4,4-TRIMETHYL-PENTANAL, 51, 4 ALDEHYDES FROM ACID CHLORIDES BY MODIFIED ROSENMUND REDUCTION 3,4,5—TRIMETHOXYBENZ-ALDEHYDE, 51, 8 ALDEHYDES FROM ACID CHLORIDES BY REDUCTION OF ESTER MESYLATES WITH SODIUM BOROHY-DRIDE CYCLOBUTANECARBOXAL-DEHYDE, 51, 11... 

ALDEHYDES BY OXIDATION OF TERMINAL OLEFINS WITH CHROMYL CHLORIDE 2,4,4-TRIMETHYLPENTANAL... 

Aldehydes by Oxidation of Terminal Olefins with Chromyl Chloride... 

In 1974, Hegedus and coworkers reported the pa]ladium(II)-promoted addition of secondary amines to a-olefins by analogy to the Wacker oxidation of terminal olefins and the platinum(II) promoted variant described earlier. This transformation provided an early example of (formally) alkene hydroamination and a remarkably direct route to tertiary amines without the usual problems associated with the use of alkyl halide electrophiles. 

Oxidation, of primary alcohols to aldehydes, 52, 5 of terminal olefins with chromyl chloride, 51, 6 of 2,4,4-trimethyl-1-pentene with chromyl chloride, 51, 4 with chromium trioxide-pyridine complex, 52, 5... 

The reactions can be carried out in aqueous solutions or biphasic mixtures of the substrates with no additional solvent, in the presence of NaOAc (pH s 11.5) at 100 °C. At this pH the resting state of the catalyst is probably the dinuclear species depicted on Scheme 8.1, which falls apart upon coordination of the substrate alcohol. In this respect the catalyst system as very similar to that for the oxidation of terminal olefins [10,11]. Good results were obtained with 30 bar of air, however, an 8 % O2/N2 mixture can also be used, which further improves the safety of the process. Recycling of the aqueous catalyst solution is possible and is especially easy in case of biphasic reaction mixtures. Taking all these features, this Pd-catalyzed oxidation of alcohols is a green process, indeed. 

A mild triple catalytic system consisting of Pd(OAc)2, hydroquinone, and a transition metal macrocycle (for example, iron phthalocyanine) was reported [243]. The catalytic effect is carried out by the interaction of Pd(II) with the substrate and the acquisition of two electrons, which are further transferred to the benzoquinone that is reduced to hydroquinone. The hydroquinone is then reorganized to benzoquinone by the 02/metal macrocycle system. The following types of transformations were carried out in mild conditions using the developed system 1,4-oxidation of conjugated dienes, oxidation of terminal olefins to methyl ketones, and allylic oxidation. 

DMF)Ru(0EP)02 (8, 135) can be formed from molecular 02, while Ti(0EP)02 (136) and Mo(TPP)(02)2 (137) can be made from peroxide addition [TPP = tetraphenylporphyrin, OEP = octaethylporphyrin]. The Ru system is ineffective for oxidation of terminal olefins at least under the mild conditions (1 atm 02, 35°C) studied thus far even the ubiquitous substrate triphenylphosphine is not oxidized catalytically because of formation of a relatively inert Ru(OEP)(PPh3)2 complex (138). The catalytic potential for 02 activation by Ru(II) porphyrins compared with Fe(II) porphyrins seems considerable, at least in principle, in view of a more readily accessible oxidation state of IV (139) this could circumvent the unfavorable one-electron reduction of 02 to superoxide (140). Such systems seem promising generally in terms of the multi-electron redox processes that 02 displays (141). 

Oxidation of terminal olefins to aldehydes. In a detailed procedure a mixture of 1.0 mole of 2,4,4-trimethyl-1 -pentene (Eastman or MCB) and 1 1. of methylene chloride is stirred mechanically in a S-l. three-necked flask fitted with a thermometer and a... 

It is surprising that the Wacker-type oxidation of 1-octene to 2-octanone is faster with the Co-salophen/zeolite catalyst than with the free complex. However, it is known that the Pd(II)-catalyzed oxidation of terminal olefins to ketones is accelerated by the presence of a catalytic amount of strong acid [1,2]. An explanation of the fester rate of the zeolite-encapsulated Co-salophen in this case is therefore that the acidic sites in the zeolite accelerate the reaction. 

Jiro Tsuji carried out many mechanistic and synthetic studies on the initial Wacker oxidation process.7-" It is now known as the Wacker-Tsuji oxidation for the oxidation of terminal olefin 1 to the corresponding methyl ketone 2 with oxygen in the presence of a catalytic amount of palladium and one equivalent of copper salt.12-" Nowadays, the Wacker-Tsuji oxidation is a standard methodology for transforming the terminal olefin to the corresponding methyl ketone.17 The reaction is so widely used that Tsuji declared that a terminal olefin could be viewed as a masked methyl ketone."... 

P450-catalyzed oxidation of terminal acetylenes to substituted acetic acids (Chapter 6) is more prone to result in heme alkylation than the oxidation of terminal olefins. The structure-activity relationships for the acetylene reaction are similar to those for terminal olefins, except that there are fewer instances in which the reaction does not result in errzyme inactivation. For example, P450 is inactivated by phenylacetylene but not delectably by styrene ", and P450 is inactivated by internal acetylenes, albeit without heme adduct formation, but not by internal olefins 22 , Catalytic oxidation of the acetylenic function is required for enzyme inactivation and terminal acetylenes give heme adducts analogous to those obtained with terminal olefins - 259 jhe salient difference in the adducts obtained with acetylenes and olefins... 

The oxidation of terminal olefins to ketones with dioxygen is catalyzed by rhodium(I) phosphine complexes. The phosphine is co-oxidized to the phosphine oxide. Mechanistic studies show that the active intermediate contains a ir-bonded olefin and dioxygen is... 

Epoxidation of olefins was catalyzed by the ruthenium(II) complex of the above perfluorinated y3-diketone in the presence of 2-methylpropanal (Scheme 50). Unfunctionalized olefins were epoxidized with a cobalt-containing porphyrin complex, and epoxidation of styrene derivatives was catalyzed by chiral salen manganese complexes (248) (Scheme 50). In the latter case, chemical yields were generally high, however, the products showed low enantiomeric excess with the exception of indene (92% ee). [Pd(C7Fi5COCHCOC7Fi5)2] efficiently catalyzed the oxidation of terminal olefins to methyl ketones with f-butylhydroperoxide as oxidant in a benzene-bromoperfluoro-octane solvent system (Scheme 50). In all these reactions, the product isolation and efficient catalyst recycle was achieved by a simple phase separation. 

Other Methods.— The palladium-catalysed oxidation of terminal olefins to methyl ketones is very efficient using 30% hydrogen peroxide in acetic acid or t-butyl alcohol. The method offers advantages in that conversions are usually high, aldehyde production is very low, and the method requires only very low concentrations of palladium [20—40p.p.m, as palladium(li) acetate], fi-Hydroxy-o-nitrophenylselenides, or their O-acyl derivatives, on oxidation with hydrogen peroxide undergo elimination to form ketones or enol esters [equation (10)]. The starting materials can be prepared easily from alkenes via their epoxides. 

The carboalumination of terminal olefins with MeaAl in the presence of chiral zirconium catalysts [bis(l-neomenthylindenyl)zirconium dichloride, bis (l-neo- so-menthyl-4,5,6,7-tetrahydroindenyl)zirconium dichloride and so on], ZACA reaction, followed by oxidation of the chiral alanes is suitable for preparing optically active alcohols with high enantioselectivity [82] (Scheme 12). 

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