Hydrogen-carbon bonds functionalization

Startg. a-peracetoxynitrile irradiated 1 hr. with a 450 w. high-pressure Hanovia lamp in terf-butanol -> product. Y 56%. F. e., also in benzene, and reiterative functionalization of unactivated hydrogen-carbon bonds by repetition of the 2-step conversion, s. D. S. Watt, Am. Soc. 95, 271 (1976). 

Beside thioamides, dithioesters are the most stable and accessible thiocarbonyl compounds. Their specific reactivity, in particular towards nucleophiUc reagents and their apphcations to the formation of carbon-carbon bonds, have already been reviewed [8]. However, as shown below, the presence of a phosphonate function alpha or beta to the thiocarbonyl group in phosphonodithioformates and phosphonodithioacetates makes these difunctional compounds very versatile building blocks. Moreover, for the phosphonodithioacetates, the substitution of the methylenic hydrogen atoms by fluorine increases again their potential as intermediates for the synthesis of modified natural and bioactive phosphorylated structures. 

With aliphatic derivatives that have a hydrogen atom bonded to the carbon atom which has the nitro, nitrite or nitrate functional group, this hydrogen atom has a mobility that makes it easy to form the corresponding anion due to the effect of a base. Unfortunately this anion is unstable and detonates immediately when dry. Even if these conditions are not fulfilled, the reaction that involves this type of intermediate is always dangerous. With aromatic nitrated derivatives the base-... 

If hydrogen gas is added to the reaction mixture of J, and 11 the hydrogenolysis reaction of thorium-to-carbon sigma bonds (J-1 22) allows interception of species 13 and thus, catalytic hydrogenation of the inserted carbon monoxide functionality. At 35 C under 0.75 atm initial H2 pressure with [JJ =9.0 x 10" M and [ 1JJ = 6.5 x 10" M, hydrogenation and isomerization are competitive and both the enolate and the alkoxide reduction product 14 are produced (eq.(13)). Under these conditions, turnover fre-... 

An exceptionally interesting example of the electrohydrocyclization reaction involves the use of allenes which are tethered to a,/S-unsaturated esters (Table 3) [19]. The chemistry takes place in a manner wherein the new carbon-carbon bond forms between the central carbon of the allene and the /S-carbon of the unsaturated ester. Of particular value is the preservation of one of the double bonds of the original allene, thereby providing functionality for further elaboration. It is important to carry out these transformations in an undivided cell, as the use of a divided cell led to hydrogenation of the olefins instead of cyclization. 

For the mixed aldol reaction to be of value in synthetic work, it is necessary to restrict the number of combinations. This can be accomplished as follows. First, if one of the materials has no a-hydrogens, then it cannot produce an enoiate anion, and so cannot function as the nucleophile. Second, in aldehyde plus ketone combinations, the aldehyde is going to be a better electrophile, so reacts preferentially in this role. A simple example of this approach is the reaction of benzaldehyde with acetone under basic conditions. Such reactions are synthetically important as a means of increasing chemical complexity by forming new carbon-carbon bonds. 

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