Alkyl fragments oxidation

The field of alkyl and aryl Co complexes in low formal oxidation states has been extensively studied, and is frequently associated with cluster chemistry.92 Alkyl and aryl ligands, with or without additional functionality, are often co-ligands with tt acceptors such as carbonyls and/or phosphines, e.g., (MeOCOCH2)Co(CO)3(PPh3).93 A simple example of a cluster is (RC)Co3(CO)9, where the triangular Co(CO)3 3 moiety is capped by the 73-alkyl fragment, which occupies the apex of a distorted Co3C tetrahedron. 

If the side chain is in an iso form, a more complex aromatic olefin forms. Isopropyl benzene leads to a methyl styrene and styrene [70], The long-chain alkylate aromatics decay to styrene, phenyl, benzyl, benzene, and alkyl fragments. The oxidation processes of the xylenes follow somewhat similar mechanisms [71, 72],... 

Since tin-containing co-catalysts are essential for the metathesis of functionalized olefins [26], it was soon discovered that 1 supported on acidic metal oxides forms metathesis catalysts that are active without additives even for functionalized olefins [26]. Standard supports are Al203-Si02, or Nb205 and the activity is related to the surface acidity [2, 3, 26]. A high metathesis activity is observed when MTO is chemisorbed on the surface. No evidence for a surface carbene species was obtained, but there appears to be a correlation between the catalytic activity and the presence of an alkyl fragment on the surface [26a-c]. 

Reactions (5)-(8) and (10) lead to the formation of stable molecules (hydrocarbons and aldehydes). Subsequent reactions of peroxy- (CnH2n+i02) and oxy-radicals (CnH2n+iO) formed in reactions (9) and (11) lead to the formation of oxygenates (alcohols, aldehydes, etc.), carbon oxides, and/or olefins. The fractions of radicals transformed into different final products depend on the reaction conditions (temperature, oxygen pressure) and on the number of carbon atoms in the alkane molecule. For example, the stability of peroxy radicals decreases with increase of the number of carbon atoms in the alkyl fragment, that is why the probability of total oxidation via their subsequent transformations decreases from methane to... 

Selenium dioxide is probably the most common reagent used to selectively oxidize an alkyl fragment, and is particularly effective for converting allylic or benzylic C—H fragments to the corresponding allylic alcohol.522 In the most common applications, carbonyl derivatives are oxidized to 1,2-dicarbonyl compounds and allylic hydrocarbons to alcohols or esters. 23... 

In the olivanic acid series of carbapenems the ( )-acetamidoethenyl grouping can be isomerised to the (Z)-isomer (19) (22) and reaction with hypobromous acid provides a bromohydrin that fragments to give a thiol of type (20) when R = H, SO H, or COCH. The thiol is not isolated but can react to provide new alkyl or alkenyl C-2 substituents (28). In the case of the nonsulfated olivanic acids, inversion of the stereochemistry at the 8(3)-hydroxyl group by way of a Mitsunobu reaction affords an entry to the 8(R)-thienamycin series (29). An alternative method for introducing new sulfur substituents makes use of a displacement reaction of a carbapenem (3)-oxide with a thiol (30). Microbial deacylation of the acylamino group in PS-5 (5) has... 

Unsymmetric allylstannanes in which the tin substituent is at the more substituted end of the allyl fragment have been obtained by oxidative elimination of primary alkyl aryl selenides which are available from the corresponding primary alcohols. This procedure was satisfactory for allylstannanes unsubstituted at the 3-position, but elimination of secondary aryl selenides gave mixtures of regioisomers33. 

In the presence of a suitably disposed /i-hydrogen—as in alkyl-substituted thiirane oxides such as 16c—an alternative, more facile pathway for thermal fragmentation is available . In such cases the thiirene oxides are thermally rearranged to the allylic sulfenic acid, 37, similarly to the thermolysis of larger cyclic and acyclic sulfoxides (see equation 9). In sharp contrast to this type of thiirane oxide, mono- and cis-disubstituted ones have no available hydrogen for abstraction and afford on thermolysis only olefins and sulfur monoxide . However, rapid thermolysis of thiirane oxides of type 16c at high temperatures (200-340 °C), rather than at room temperature or lower, afforded mixtures of cis- and trans-olefins with the concomitant extrusion of sulfur monoxide . The rationale proposed for all these observations is that thiirane oxides may thermally... 

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