Birch reduction tetrahydro

Dibenzothiophene, 1,2,3,4-tetrahydro-4-keto-synthesis, 4, 905 Dibenzothiophenes alkylation, 4, 724 Birch reduction, 4, 775 C NMR, 4, 11... 

Birch reductions in ammonia-tetrahydro-furan-/-butyl alcohol, 49... 

The following examples may be cited to illustrate these generalizations. />-Toluic acid under conditions of the Birch reduction essentially as given in this procedure yields mainly 1,2,3,4-tetrahydro-/>-toluic acid (cis and trans) plus minor amounts of... 

The second approach (224-226) employs O-methylhexadehydroyohimbine (420), prepared from spiroindeno-2-(l -tetrahydro-0-carboline)-l-onederivative 416 by photolysis and subsequent reduction, as the key intermediate. The side product (418) of the photolysis was also utilized for the preparation of 420 via subsequent phosphoryl chloride treatment and sodium borohydride reduction. Birch reduction of 420 resulted in enol ether 421, which could be transformed to 15,16-didehydroyohimbinone (410), prepared previously by Szantay et al. (74, 221) as a universal precursor of the synthesis of yohimbine-type alkaloids. 

Jenny and Reiner 107> obtained the di- and tetrahydro compounds 153 and 154 by Birch reduction of [2.2]paracyclophane. On the basis of spectroscopic findings, the authors postulate the configuration 153 a A, for the dihydro compound, where the benzene rings are slightly distorted in a tublike fashion. 

The Birch reduction of dibenzofuran is reported to give 1,4-dihydro-dibenzofuran. The electrochemical reduction of dibenzofuran by solvated electrons is reported to produce a dihydrodibenzofuran and a tetrahydro-dibenzofuran, both of unspecified structure. Treatment of dibenzofuran with W-7 Raney nickel in boiling methanol gave a moderate yield of trans-2-phenylcyclohexanol, whereas treatment of dibenzofuran with Raney nickel alloy and aqueous sodium hydroxide gave a low yield of 2-biphenylol. ... 

Birch reduction of phenanthrene or 9-alkylphenanthrenes results in tetrahydro derivatives, but 9,10-dihydro derivatives are obtained in high yield by Li/NH3 reduction of phenanthrenes substituted by a 9-trimethylsilyl group (equation I). The trimethylsilyl group of 1 can be removed in quantitative yield with Bu4NF in... 

Table 11 shows some representative results from the cathodic reduction of some aromatic hydrocarbons. These include cases with Ei j2 near the cathodic limit or in the discharge region of the SSE (benzene, toluene) and cases with Ex j2 at considerably more positive potential (naphthalene, anthracene again we must anticipate the discussion of reactivity and refer to Table 21). Reactions nos. 1, 2, 6, and 7 immediately demonstrate one difficulty with such studies in that the catholyte of a divided cell becomes strongly basic as electrolysis progresses. In sufficiently basic medium, the initial product, a 1,4-dihydro derivative (cf. the Birch reduction Birch and Subba Rao, 1972), will rearrange to a conjugated system which, in contrast to the 1,4-dihydro derivative, is further reducible to the tetrahydro product (nos. 1 and 6). In a non-divided cell the acid production at the anode balances the base production and thus only a little rearrangement occurs. It is therefore not a trivial problem to find out if the tetrahydro product is formed from the conjugated dihydro product, formed directly or by rearrangement [eqn (78)].

Cyclic non-conjugated (139 and 140) or conjugated (141 and 142) dienamines may be obtained by Birch reduction of the corresponding aromatic amine552,553. The preferred conditions involve the use of lithium and t-pentyl alcohol rather than ethanol, since the latter tends to give a considerably higher proportion of the further reduced tetrahydro derivative554. 

Aromatic ring reduced morphinans and isomorphinans have been reported/52 Birch reduction of 3-methoxy- N-methylmorphinan (61a) and the corresponding isomorphinan (61b) gave the respective l,2,3,4-tetrahydro-3-oxo-derivatives (62a and 62b) together with small amounts of the desoxo compounds 63a and 63b. The morphinan and isomorphinan precursors (60a and 60b) were derived from (58)(53) or dihydrothebainone (59), according to Scheme 3.8. In the RTF test, no significant activity was observed for 62a or 62b. 

Benzene [52], anisole, l,2,3,4-tetrahydro-6-methoxynaphthalene [53], and estradiol-3-methyl ether [54] have been reduced in a similar cathodic Birch reduction in water [52], aqueous diglyme, and aqueous tetrahydrofuran with TBA as electrolyte at room temperature TBA(Hg) has been proposed [53,54] to be a mediator in the reduction shown in Eq. (1) ... 

Oxygenated isoquinolinium derivatives (34) have been prepared by isomerization of dihydroindeno-azirinones (33). Studies are reported on the Birch reduction of l,2,3,4-tetrahydro-2-methylisoquinoline and its 6- and 7-methoxy-analogues. ... 

Takano et al. <78JOC4l69> prepared an emetine precursor (316) through cleavage with base of the a-diketone monothioketal derivative (315), obtained by Birch reduction of the tetrahydro-protoberberine system (314) followed by functionalization as shown in Scheme 71. 

Birch reduction of tetrahydro-2-pyranyl ethers Protection of hydroxyl groups Sec. alcohols from ketones... 

The unsaturated syn-cis-ketone (145) described in Scheme 94, on catalytic hydrogenation in the presence of hydrogen bromide, was converted almost exclusively into the cis-syn-cis-isomer (152), while Birch reduction led to the new trans-syn-cis-isomer (150). Dehydrogenation of ketone (145) in a neutral medium gave a mixture of the isomers (150) and (152). The structures of the tetrahydro derivatives of the ketone (140) were shown by their mutual interconversions via the 11-oxo derivatives and by the transformation of some of them into natural steroids of known configuration (see below). 

The Birch-type electrochemical reduction (460) (461) has been shown to proceed through the action of tetra-butylammonium amalgam in the steps (460)— (462)— (463), in contrast to a direct electron transfer from the electrode to the aromatics (Scheme 158) [548]. The preparative-scale reduction of anisole, of l,2,3,4-tetrahydro-6-methoxynaphthalene, and several aromatic steroids is performed in an H20-Bu4N0H-(Hg) system. The unique aspect of the reduction is the proposed formation of a tetrabutylammo-nium amalgam complex, BU4N (Hg) (465)... 

Solutions of Group I metals in the lower molecular weight amines are more potent reductants than those in liquid ammonia, and as a general rule substrates are more extensively reduced than by the Birch method. o Naphthalene (49 Scheme 48), for example, is reduced by a solution of lithium in ethylamine to a 1 1 mixture of A W- and A -octalins (214) and (215). If ethylenediamine is employed as the medium, the completely saturated decahydronaphthalene is formed, while the proportion of (215) may be increased to 80% by utilizing a (1 1) mixture of ethylamine with dimethylamine. The formation of the more-substituted alkene appears to be a general result for such primary and secondary amine mixtures and has been used to good effect in the reduction of both toluene and cumene to their 3,4,5,6-tetrahydro derivatives (216) and (217), respectively, in ca. 80% yields. A comprehensive review of these kinds of reducing systems, which also draws comparisons with the Birch method, is available,but more recent-... 

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