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Clemmensen reduction is a chemical reaction described as a reduction of ketones or aldehydes to alkanes using zinc amalgam and concentrated hydrochloric acid (HCl). [1] [2] This reaction is named after Erik Christian Clemmensen, a Danish-American chemist. [3] Scheme 1: Reaction scheme of Clemmensen Reduction.
Enantioselective ketone reductions convert prochiral ketones into chiral, non-racemic alcohols and are used heavily for the synthesis of stereodefined alcohols. [ 1 ] Carbonyl reduction, the net addition of H 2 across a carbon-oxygen double bond, is an important way to prepare alcohols.
This reductive coupling can be viewed as involving two steps. First is the formation of a pinacolate (1,2- diolate ) complex, a step which is equivalent to the pinacol coupling reaction . The second step is the deoxygenation of the pinacolate, which yields the alkene , this second step exploits the oxophilicity of titanium.
Aldehydes and ketones can be reduced respectively to primary and secondary alcohols. In deoxygenation, the alcohol group can be further reduced and removed altogether by replacement with H. Two broad strategies exist for carbonyl reduction. One method, which is favored in industry, uses hydrogen as the reductant.
This reaction sequence is thus a condensation reaction since there is a net loss of HCl when the two reactant molecules join. [7] Arrow-pushing mechanism for the Darzens reaction. If the starting halide is an α-halo amide, the product is an α,β-epoxy amide. [8] If an α-halo ketone is used, the product is an α,β-epoxy ketone. [2]
An aldol condensation is a condensation reaction in organic chemistry in which two carbonyl moieties (of aldehydes or ketones) react to form a β-hydroxyaldehyde or β-hydroxyketone (an aldol reaction), and this is then followed by dehydration to give a conjugated enone. The overall reaction equation is as follows (where the Rs can be H)
The Tsuji-Wacker oxidation oxidizes terminal olefin to the corresponding methyl ketone under the Wacker process condition. Almost identical to that of Wacker Process, the proposed catalytic cycle [ 32 ] (Figure 1) begins with complexation of PdCl 2 and two chloride anions to PdCl 4 , which then undergoes subsequent ligand exchange of two ...
Nahm and Weinreb also reported the synthesis of aldehydes by reduction of the amide with an excess of lithium aluminum hydride (see amide reduction). The Weinreb–Nahm ketone synthesis. The major advantage of this method over addition of organometallic reagents to more typical acyl compounds is that it avoids the common problem of over-addition.