Analogous reactions

The 2-anilinoselenazoles follow an analogous reaction path. The entry of bromine into the 5-position is in agreement as seen in Scheme 35. The 2-anilino-4-phenylselenazole gives a 5-bromo derivative by bromination. It is not identical with either of the bromo derivatives prepared by direct synthesis (Scheme 35) (99). 

Analogous reactions take place in other solvents which like water contain an —OH group Solvolysis in methanol (methanolysis) gives a methyl ether... 

Friedel-Crafts acylation An analogous reaction occurs when acyl halides react with benzene in the presence of alumi num chloride The products are acylben zenes... 

Amines undergo an analogous reaction to yield acetamides, the more basic amines having the greater activity ... 

The analogous reaction with ammonia leads ultimately to sihcon nitride. In the past, hydrocarbon soluble fractions of the ammonolysis were iacorrecdy referred to as sihcon diimide. This improper designation occasionally persists as of the mid-1990s. 

The analogous reaction between anhydrides and alkoxysilanes also produces acyloxysilanes. The direct reaction of acids with chlorosilanes does not cleanly lead to full substitution. Commercial production of methyltriacetoxysilane direcdy from methyltrichlorosilane and acetic acid has been made possible by the addition of small amounts of acetic anhydride or EDTA, or acceptance of dimethyltetraacetoxydisiloxane in the final room temperature vulcanising (RTV) appHcation (41—43). A reaction that leads to the formation of acyloxysilanes is the interaction of acid chlorides with silylamides. 

Analogous reactions form sodiummethyldithiocarbamate [137-42-8] from methylamine, and disodiumethylenebis(dithiocarbamate) [142-59-6] from ethylenediamine. Iron, manganese, and 2iac salts can be prepared from the sodium salts heavy metals form characteristically colored compounds with dithio c arb amate s. 

There are a variety of reaction systems that allow the formation of cellulose trinitrate [9046-47-3]. HNO in methylene chloride, CH2CI2, yields a trinitrate with essentially no degradation of the cellulose chain (53). The HNO /acetic acid/acetic anhydride system is also used to obtain the trinitrate product with the fiber stmcture largely intact (51,52). Another polymer analogous reaction utilises a 1 1 mixture of HNO and H PO with 2.5% P2O5 to achieve an almost completely nitrated product (54). 

Enhanced Reaction Kinetics. For reactions involving tritium, the reaction rates are frequendy larger than expected because of the ionising effects of the tritium P-decay. For example, the uncataly2ed reaction 2T2+O2 — 2X20 can be observed under conditions (25°C) for which the analogous reaction of H2 or D2 would be too slow for detection (30). 

Because of the increased importance of inductive electron withdrawal, nucleophilic attack on uncharged azole rings generally occurs under milder conditions than those required for analogous reactions with pyridines or pyridones. Azolium rings are very easily attacked by nucleophilic reagents reactions similar to those of pyridinium and pyrylium compounds are known azolium rings open particularly readily. 

Substituted imidazoles can be acylated at the 2-position by acid chlorides in the presence of triethylamine. This reaction proceeds by proton loss on the (V-acylated intermediate (241). An analogous reaction with phenyl isocyanate gives (242), probably via a similar mechanism. Benzimidazoles react similarly, but pyrazoles do not (80AHC(27)24l) cf. Section 4.02.1.4.6). 

Reaction of a hydrazide (128) with phosgeneiminium chloride (115) led to the 2-dimethylamino-l,3,4-oxadiazole (129) in 90% yield (75AG(E)806). The 1,3,4-thiadiazole system was also obtained in an analogous reaction in which the dithioimidate (130) underwent reaction with the thiohydrazide (131). Depending on the nature of X in (131), the 2-substituent in the resultant 1,3,4-thiadiazole (132) may be varied (80ZC413). Although (130)... 

Azetidines under analogous reaction conditions to those above result in six-membered ring formation. However, diketene (472), an oxetan-2-one, offers considerable promise for five-membered heterocycle formation. With hydroxylamine the 3-methylisoxazolin-5-one (473) was formed. Phenylhydrazine gave the corresponding 3-methyl-l-phenylpyrazolin-5-one. 

The synthetic procedure described is based on that reported earlier for the synthesis on a smaller scale of anthracene, benz[a]anthracene, chrysene, dibenz[a,c]anthracene, and phenanthrene in excellent yields from the corresponding quinones. Although reduction of quinones with HI and phosphorus was described in the older literature, relatively drastic conditions were employed and mixtures of polyhydrogenated derivatives were the principal products. The relatively milder experimental procedure employed herein appears generally applicable to the reduction of both ortho- and para-quinones directly to the fully aromatic polycyclic arenes. The method is apparently inapplicable to quinones having an olefinic bond, such as o-naphthoquinone, since an analogous reaction of the latter provides a product of undetermined structure (unpublished result). As shown previously, phenols and hydro-quinones, implicated as intermediates in the reduction of quinones by HI, can also be smoothly deoxygenated to fully aromatic polycyclic arenes under conditions similar to those described herein. 

Reduction of phenanthrene-9,10-dione with HI in acetic acid afforded 9-hydroxyphenanthrene as sole product, while an analogous reaction without acetic acid furnished phenanthrene essentially quantitatively. 

High vacuum sublimation of the 3-monobenzoate of (32) or tosylchloride dehydration gives 3/ -benzoyloxy-7-methylenecholest-5-ene (33). The configuration of (32) is probably as shown since 7a-hydroxy steroids dehydrate readily to yield homoannular dienes. In an analogous reaction ethyl and iso-butyl Grignard reagents give alkylidene compounds as the only isolated products. 

Bromination of the enolate anion from the reaction of 3j -acetoxypregna-5,16-dien-20-one (1) with methylmagnesium bromide in the presence of cuprous chloride affords (after treatment with sodium iodide to dehalo-genate any 5,6-dibromide) a mixture of 17a-bromo- and 17)5-bromo-16a-methyl compounds (11) and (12) in a ratio 9 1. The 17a-iodides can be obtained in an analogous reaction. 

Oxidation of 17j5-acetoxy-5a-androstan-3-one (1) by chromium trioxide in acetic acid at 55-65° gives the 2,3-seco acid (2). Conversion of the seco acid to its anhydride followed by pyrolysis and distillation gives the A-nor-2-ketone (3) in 45% overall yield. Analogous reactions have been carried... 

Hydrolysis of the acetate (71) followed by Oppenauer oxidation gives B-norcholest-4-en-3-one in high yield. An analogous reaction sequence can be used to prepare B-norprogesterone and derivatives of B-nortestosterone from pregnenolone acetate and dehydroepiandrosterone acetate, respectively."" ... 

The analogous reactions of 5-nitro- [227] and 5-bromofuran-2-carboxylic acids [228] lead to addition of two fluorine atoms and replacement of the nitro group... 

Hexafluoropropene is converted to its 1,2-epoxide in 55% yield by bubbling through a solution of chromium tnoxide in fluorosulfonic acid [8], the analogous reaction with a mixture of chromium trioxide and dichromium tnoxide gives pentafluoroacetonyl fluorosulfate [.5] (equation 6)... 

Generally, additions of halogens to fluoroalkenes are less stereoselective than the analogous reactions with nonfluorinated systems. The stereochemical mode of addition can be either anti or syn Partitioning between these paths is determined... 

Analogous reactions under free-radical conditions show a preference for the erythro isomer when X = Cl, however when X = tnfluoromethyl, the reaction shows essentially no stereoselectivity [S] (Table 3)... 

Silver trifluoroacetate is used in a one step synthesis of bicyclo[3 2 2]nona-6,8-diene-3-one from 2-methoxyallyl bromide and benzene [50] (equation 23) Analogous reactions of toluene, p-xylene, and mesitylene yield the corre spending substituted bicyclo[3 2 2]noiia-6,8-diene-3-ones [50]... 

The reaction of benzenesulfonic acid with sodium hydroxide (first entry in Table 24.3) proceeds by the addition-elimination mechanism of nucleophilic aromatic substitution (Section 23.6). Hydroxide replaces sulfite ion (S03 ) at the carbon atom that bear s the leaving group. Thus, p-toluenesulfonic acid is converted exclusively to p-cresol by an analogous reaction ... 

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