Sodium reductions with

Piperitone is of considerable technical im portance. It is a colourless oil of a pleasant peppermint-like smell. (-)-Piperilone has b.p. 109-5-110-5 C/I5mm. Piperitone yields thymol on oxidation with FeCl. On reduction with hydrogen in presence of a nickel catalyst it yields menthone. On reduction with sodium in alcoholic solution all forms of piperitone yield racemic menthols and womenthols together with some racemic a-phel)andrene. 

SchifT s bases A -Arylimides, Ar-N = CR2, prepared by reaction of aromatic amines with aliphatic or aromatic aldehydes and ketones. They are crystalline, weakly basic compounds which give hydrochlorides in non-aqueous solvents. With dilute aqueous acids the parent amine and carbonyl compounds are regenerated. Reduction with sodium and alcohol gives... 

Extremely dry (or super-dry ) ethyl alcohol. The yields in several organic preparations e.g., malonic ester syntheses, reduction with sodium and ethyl alcohol, veronal synthesis) are considerably improved by the use of alcohol of 99-8 per cent, purity or higher. This very high grade ethyl alcohol may be prepared in several ways from commercial absolute alcohol or from the product of dehydration of rectified spirit with quicklime (see under 4). 

Nitrophenylhydrazine may be similarly prepared from p-nitroplienyl-diazonium chloride by reduction with sodium or ammonium sulphite ... 

Reduction with sodium in alcohol was unsuccessful (54). The introduction of lithium aluminium hydride has provided an elegant method for the reduction of thiazole esters to hydroxythiazoles for example, ethyl 2-methyl-4-thiazolecarboxylate (11 with lithium aluminium hydride in diethyl ether gives 2-methyl-4-(hydroxymethyl)thiazole (12) in 66 to 69% yield (Scheme 7) (53),... 

Reduction to alcohols (Section 15 2) Aide hydes are reduced to primary alcohols and ketones are reduced to secondary alcohols by a variety of reducing agents Catalytic hydrogenation over a metal catalyst and reduction with sodium borohydride or lithium aluminum hydride are general methods... 

A schematic illustration of a typical inlet apparatus for separating volatile hydrides from the analyte solution, in which they are generated upon reduction with sodium tetrahydroborate. When the mixed analyte solution containing volatile hydrides enters the main part of the gas/liquid separator, the volatiles are released and mix with argon sweep and makeup gas, with which they are transported to the center of the plasma. The unwanted analyte solution drains from the end of the gas/liquid separator. The actual construction details of these gas/liquid separators can vary considerably, but all serve the same purpose. In some of them, there can be an intermediate stage for removal of air and hydrogen from the hydrides before the latter are sent to the plasma. 

AHylestrenol (37) is prepared from (32), an intermediate in the synthesis of norethindrone. Treatment of (32) with ethanedithiol and catalytic boron trifluoride provides a thioketal. Reduction with sodium in Hquid ammonia results in the desired reductive elimination of the thioketal along with reduction of the 17-keto group. Oxidation of this alcohol with chromic acid in acetone followed by addition of aHyl magnesium bromide, completes the synthesis... 

These reactions are usehil for the preparation of homogeneous difunctional initiators from a-methylstyrene in polar solvents such as tetrahydrofuran. Because of the low ceiling temperature of a-methylstyrene (T = 61° C) (26), dimers or tetramers can be formed depending on the alkaU metal system, temperature, and concentration. Thus the reduction of a-methylstyrene by sodium potassium alloy produces the dimeric dianionic initiators in THF (27), while the reduction with sodium metal forms the tetrameric dianions as the main products (28). The stmctures of the dimer and tetramer correspond to initial tail-to-tail addition to form the most stable dianion as shown in equations 6 and 7 (28). 

Higher nitroalkanes are prepared from lower primary nitroalkanes by a one-pot synthesis (69). Successive condensations with aldehydes and acylating agents are followed by reduction with sodium borohydride. Overall conversions in the 75—80% range are reported. 

The compound can be prepared from 2,4,6-trinitrophenol (picric acid [88-89-1]) by reduction with sodium hydrosulfide (163), with ammonia —hydrogen sulfide followed by acetic acid neutralization of the ammonium salt (164), with ethanolic hydrazine and copper (165), or electrolyticaHy with vanadium sulfate in alcoholic sulfuric acid (159). Heating 4,6-dinitro-2-benzamidophenol in concentrated HQ. at 140°C also yields picramic acid (166). 

Later, a completely different and more convenient synthesis of riboflavin and analogues was developed (34). It consists of the nitrosative cyclization of 6-(A/-D-ribityl-3,4-xyhdino)uracil (18), obtained from the condensation of A/-D-ribityl-3,4-xyhdine (11) and 6-chlorouracil (19), with excess sodium nitrite in acetic acid, or the cyclization of (18) with potassium nitrate in acetic in the presence of sulfuric acid, to give riboflavin-5-oxide (20) in high yield. Reduction with sodium dithionite gives (1). In another synthesis, 5-nitro-6-(A/-D-ribityl-3,4-xyhdino) uracil (21), prepared in situ from the condensation of 6-chloro-5-nitrouracil (22) with A/-D-ribityl-3,4-xyhdine (11), was hydrogenated over palladium on charcoal in acetic acid. The filtrate included 5-amino-6-(A/-D-ribityl-3,4-xyhdino)uracil (23) and was maintained at room temperature to precipitate (1) by autoxidation (35). These two pathways are suitable for the preparation of riboflavin analogues possessing several substituents (Fig. 4). 

Synthesis. The parent compound, bora2iae [6569-51-3] is best prepared by a two-step process involving formation of B-trichlorobora2iQe followed by reduction with sodium borohydride. These reactions have been studied ia some detail (96). 

Dithiols, like diols, have been protected as 5,5 -methylene, 5,5 -isopropylidene, and 5,5 -benzylidene derivatives, formed by reaction of the dithiol with formaldehyde, acetone, or benzaldehyde, respectively. The methylene and benzylidene derivatives are cleaved by reduction with sodium/ammonia. The isopropylidene and benzylidene derivatives are cleaved by mercury(II) chloride with sodium/ ammonia the isopropylidene derivative is converted to a monothio ether, HSCHR-CHRSCHMe2- ... 

Two classes of charged radicals derived from ketones have been well studied. Ketyls are radical anions formed by one-electron reduction of carbonyl compounds. The formation of the benzophenone radical anion by reduction with sodium metal is an example. This radical anion is deep blue in color and is veiy reactive toward both oxygen and protons. Many detailed studies on the structure and spectral properties of this and related radical anions have been carried out. A common chemical reaction of the ketyl radicals is coupling to form a diamagnetic dianion. This occurs reversibly for simple aromatic ketyls. The dimerization is promoted by protonation of one or both of the ketyls because the electrostatic repulsion is then removed. The coupling process leads to reductive dimerization of carbonyl compounds, a reaction that will be discussed in detail in Section 5.5.3 of Part B. 

Willstatter and Bode converted tropinone into (/(-ecgonine by treating sodium tropinone with carbon dioxide and sodium, when it yielded sodium tropinonecarboxylate. This on reduction with sodium in alcohol gave some dZ-i/i-ecgonine (p. 97), which on esterification with methyl alcohol and benzoylation yielded a dhcocainc. A simpler synthesis of ( -eegonine was achieved by Willstatter and Bommer, and reference is made on p, 80 to this and other processes, some of which have been protected by patents. These improvements having enabled the prepara-... 

On reduction with sodium in amyl alcohol deoxymatrine (C45H24N2)j, prisms, m.p. 162°, is produced, which with red phosphorus and hydriodic... 

Nitrogen cannot be eliminated from the latter by further methylation, but (VIII) on catalytic hydrogenation has its vinyl group converted into ethyl and the product, on methylation followed by reduction with sodium amalgam, yields 6-dimethylamino-3 4 3 4 -tetramethoxy-6 -ethyl-a)3-diphenylethane (X), and this, on repetition of the methylation, and reduc-... 

On oxidation with permanganate, methylharmaline is converted into a neutral substance, CiaHj O Na, m.p. 228°, which, on reduction with sodium and n-butyl alcohol yields A -methyltetrahydronorharmine (XVII),... 

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