Reduction reactions Birch

A number of A -3-keto-D-seco-17-alcohols have also been prepared. Base-promoted cleavage of the d ring of oestrone (114a), followed by esterification, lithium aluminium hydride reduction, and Birch reaction, gave, after mild... 

It is possible to form partially reduced bicyclic and tricyclic aromatic derivatives by this method. One of the more interesting synthetic features of the Birch reduction is the ability to alkylate the carbanionic intermediate generated by the electron-transfer reaction. Birch reduction of 517, for example, gave a mixture of 518 and 519 in 96% yield upon addition of 2-(2-bromo-5-methoxyphenyl)-l-iodoethane to the initially produced anion. 

This reaction is related to the Benkeser Reduction and Birch Reduction. 

Substituent groups on the benzene ring influence the course of the reaction. Birch reduction of methoxybenzene (anisole) leads to the formation of 1-methoxy-1,4-cyclohexadiene, a compound that can be hydrolyzed by dilute acid to 2-cyclohexenone. This method provides a useful synthesis of 2-cyclohexenones ... 

Reduction of Aromatic Compounds 710 [ A MECHANISM FOR THE REACTION ] Birch Reduction 710... 

Beyer Method for Quinolines Biginelli Reaction Birch Reduction... 

Reactions. Birch reduction of 2-furoic acid with lithium in liquid ammonia gives the 2,5-dihydro-compound (131) in 90% yield. Hydrogenation of the vinyl-furans (132 R = CO2H, C02Me, Ac, or COPh) in the presence of nickel bromide occurs selectively at the exocyclic double bond. Anodic methoxylation of 2-(2-thienylmethyl)-furan yields a mixture of geometrically isomeric adducts... 

Tran orm-based or long-range strategies The retrosynthetic analysis is directed toward the application of powerful synthesis transforms. Functional groups are introduced into the target compound in order to establish the retion of a certain goal transform (e.g., the transform for the Diels-Alder reaction, Robinson annulation, Birch reduction, halolactonization, etc.). 

Birch Reductions reduction of aromatic rings Organic Reactions 1976, 23, 1. Tetrahedron 1986, 42, 6354. Cornprehensice Organic Synthesis 1991, voJ. 8, 107. 

Analysis The strategy for any modem syntheses of these compounds would be based on the Diels-Alder reaction or the Birch reduction ... 

The use of reducing metals nowadays is mainly restricted to acyloin and pinacol coupling reactions (see p. 53f.) and Birch reductions of arenes (A.A. Akhrcm, 1972 see p. 103f.) and activated C—C multiple bonds (see p. 103f.). 

The Birch reductions of C C double bonds with alkali metals in liquid ammonia or amines obey other rules than do the catalytic hydrogenations (D. Caine, 1976). In these reactions regio- and stereoselectivities are mainly determined by the stabilities of the intermediate carbanions. If one reduces, for example, the a, -unsaturated decalone below with lithium, a dianion is formed, whereof three different conformations (A), (B), and (C) are conceivable. Conformation (A) is the most stable, because repulsion disfavors the cis-decalin system (B) and in (C) the conjugation of the dianion is interrupted. Thus, protonation yields the trans-decalone system (G. Stork, 1964B). 

Section 1111 An example of a reaction m which the ring itself reacts is the Birch reduction The ring of an arene is reduced to a nonconjugated diene by treatment with a Group I metal (usually sodium) m liquid ammonia m the presence of an alcohol... 

Birch leaf extract Birch reduction Birch-type reactions Bird feathers Bird repellents Bireactive dyes Birkeland-Eyde process Birnessite [1244-32-5] b-Bisabolene [495-61-4]... 

Thiophene, 3-pentadeuterophenyl-chemical shifts, 4, 730 Thiophene, 2-phenyl-oxidation, 4, 800 phototranspositions, 4, 743 rearrangement, 4, 42 reduction, 4, 775 synthesis, 4, 865, 914 UV spectrum, 4, 735 Thiophene, 3-phenyl-photochemical rearrangements, 4, 735 phototranspositions, 4, 743 lsmeier formylation, 4, 759 Thiophene, 2-pivaloyl-Birch reduction, 4, 775 Thiophene, polybromo-reactivity, 4, 829 Thiophene, polylithio-synthesis, 4, 831 Thiophene, (propargylthio)-rearrangement, 4, 746 Thiophene, 2-(3-pyridinyl)-synthesis, 4, 781 Thiophene, 2-(5-pyrimidinyl)-synthesis, 4, 781 Thiophene, 3-pyrrolidinyl-cycloaddition reactions, 4, 68 with dimethyl acetylenedicarboxylate, 4, 788-789... 

The Birch reduction of a benzenoid compound involves the addition of two electrons and two protons to the ring. The order in which these additions occur has been the subject of both speculation and study. Several reviews of the subject are available and should be consulted for details. The present discussion is concerned with summarizing data that is relevant to understanding the reaction from the preparative point of view. For convenience, reaction intermediates are shown without indicating their solvation by liquid ammonia. This omission should not obscure the fact that such solvation is largely responsible for the occurrence of the Birch reduction. 

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