The reduction of some methyl phenyl ketones, the corresponding carbinols, and 2-methyl-2-phenyl-1 : 3-dioxolans with sodium or potassium and alcohols in liquid ammonia

Pinder, A. R.; Smith, Herchel

doi:10.1039/jr9540000113

Cited by 26 publications

(12 citation statements)

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“…On the other hand, Li and Na in liquid NH 3 reduce allylic and benzylic alcohols, ethers or acetals [99] , due to the highly reactive allylic or benzylic C − O bond. Thus, the benzylic acetal (87) is reduced to the compound (88) without over -reduction using Na in NH 3 and methanol [100] , but under the same reaction conditions the allylic alcohol (89) leads to bicycle (90) , after rearrangement (Scheme 17.31 ) [101] .…”

Section: Reduction Of C -O To C-h Bondsmentioning

confidence: 99%

Dissolving Metals

Yus

Foubelo

2008

Modern Reduction Methods

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17 IntroductionDissolving metals have been used extensively as reducing agents for more than a century but today they have been partially displaced from the central fi eld of organic synthesis by the use of other more selective methodologies, such as metal hydrides [1] and catalytic hydrogenations [2] . However, dissolving metals are still of interest for the selective reduction of specifi c polar functional groups (such as hindered cyclic ketones) and the reductive cleavage of some activated bonds [3] .Regarding the mode of action of electropositive metals in reduction processes, it is generally assumed that an initial single -electron transfer ( SET ) from the metal to the organic substrate takes place to give a radical anion [4] . Depending on the organic substrate and on the reaction conditions (mostly on the solvent), the highly reactive resulting radical anion can then decompose via a number of different routes. For instance, for compounds (I) with multiple C = X bonds (X = CR 2 , O, NR, S), the radical anion (II) could be protonated in the presence of a proton source (the solvent) to give a new radical (III) , which after a further SET from the metal, and further protonation of the resulting anion (IV) , would lead to the reduced product (V) . In the absence of a proton source, coupling of two radical anions (II) can occur to give fi rst the dianionic species (VI) and, after hydrolysis, compounds of type (VII) . Organic substrates (VIII) with activated bonds X − Y (X = CR 3 , OR, SR, NR 2 ; Y = CR 3 , OR, SR, NR 2 , Hal (F, Cl, Br, I)) also undergo reductive cleavage by means of electropositive metals through a SET mechanism. In this case, the initially formed radical anion (IX) suffers the activated X − Y bond scission to generate a radical (X) and an anion (XI) . Radical (X) would be converted to an anion after a new electron transfer from the metal, and fi nal protonation would yield the corresponding reduced products (XII) and (XIII) , respectively (Scheme 17.1 ).Most of the reductions by means of dissolving metals have been performed using highly electropositive metals, such as Li, Na and K, in liquid NH 3 as solvent. Less electropositive metals (Mg, Ca, Sr, Ba, Ni, Cu, Zn, In, Sn, Pb) have also been used, so by choosing the appropriate metal, solvent and cosolvent it is possible to

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Section: Reduction Of C -O To C-h Bondsmentioning

confidence: 99%

Dissolving Metals

Yus

Foubelo

2008

Modern Reduction Methods

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“…22 The furan nucleus also promotes 'benzylic' hydrogenolysis with lithium in ammonia in the absence of proton donors. 18 -20 The fission process probably occurs after two electrons have been added to the ring;18 proton donors are not required and may, when p-methoxy groups are present, promote reduction of the ring instead.…”

Section: Reduction With Dissolving Metalsmentioning

confidence: 99%

“…Norcamphor isobutylene ketal appears (NMR) to be a nearly equal mixture of the isomers (21) and (22) (Scheme 6),95 but it is reduced as though it were only (21), reacting via a retention mechanism. The reduction is very slow (168 h) and it is this author's view that one cannot exclude the possibility that (22) is not reduced at all but is isomerized to replace (21) as it is consumed (a few such isomerizations have been observed).…”

Section: Dioxolanes and Dioxanesmentioning

confidence: 99%

Reduction of Acetals, Azaacetals and Thioacetals to Ethers

Brewster

1991

Comprehensive Organic Synthesis

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“…[3][4][5][6][7][8] We were seeking a simple and environmentally benign synthesis of benzophenone and acetophenone ethylene ketals. Most of the reported methods that avoided the drawbacks of the traditional protection methods (eg.…”

Section: Methodsmentioning

confidence: 99%

Microwave assisted synthesis of benzophenone and acetophenone ethylene ketals

Lukács¹,

Porcs-Makkay²,

Komáromi³

et al. 2007

Arkivoc

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Dedicated to Professor Csaba Szántay on the occasion of his 80th birthdayAbstract A simple and convenient synthesis of acetophenone and benzophenone ethylene ketals was elaborated by performing the reaction of ethylene glycol in toluene in the presence of PTSA, under microwave irradiation with simultaneous removal of the water so formed. Under these conditions 100 % conversion and high yields were obtained within short reaction times.

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The reduction of some methyl phenyl ketones, the corresponding carbinols, and 2-methyl-2-phenyl-1 : 3-dioxolans with sodium or potassium and alcohols in liquid ammonia

Cited by 26 publications

References 0 publications

Dissolving Metals

Dissolving Metals

Reduction of Acetals, Azaacetals and Thioacetals to Ethers

Microwave assisted synthesis of benzophenone and acetophenone ethylene ketals

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