Phosphorous acid reaction with aromatic compounds

The first step of the reaction involves iodination of the aromatic compound with the triiodide salt in the presence of water as a solvent. The water should contain from 0.7 to 1.25 molar equivalents of a hydroxide, preferably an alkali metal hydroxide, and from 1-2 molar-equivalents of an alkali metal triiodide (e.g. iodine plus sodium iodide). The aqueous solvent should also contain from 0.1 to 20 mole % of an acid catalyst, which may be a mineral acid such as sulfuric, hydrochloric or phosphoric acid. Reaction is carried out at temperatures ranging from 20°-120° C. If the starting compound contains a nuclear substituent, iodination will occur in the ortho or para position on the nuclear ring. 

Since A,A -disubstituted hydrazines are readily available from a variety of sources (see Volume I, Chapter 14), their dehydrogenation constitutes a widely applicable route to both aliphatic and aromatic azo compounds. Such oxidative procedures are of particular value in the aliphatic series because so many of the procedures applicable to aromatic compounds, such as the coupling with diazonium salts, have no counterpart. The oxidation reactions permit the formation not only of azoalkanes, but also of a host of azo compounds containing other functional groups, e.g., a-carbonyl azo compounds [83], a-nitrile azo compounds [84], azo derivatives of phosphoric acid [85], phenyl-phosphoric acid derivatives [86],... 

The first attempts to control a synthetic process using multifunctional monomers were published in 1967/68 by Stille and co-workers [9-12]. They condensed 2,5-disubstituted 1,4-benzoquinones 2 with various tetra-functional aromatic compounds 1 containing amino-, hydroxy- and chloro- functionalities. When carrying out the reaction at high tanperature in polar, aprotic solvents such as HMPT (hexamethyl phosphoric acid triamide) they immediately ob-... 

Synthesis of Phosphoric Acids and their Derivatives. - Among various approaches to phosphate esters the phosphorylation of phenols with dialkyl cyanophosphonate and the synthesis of triaryl phosphates under phase-transfer conditions are worthy of mention. Mixed trialkyl phosphates are also reported to be formed by brief cathodic electrolysis of the reaction of dialkyl phosphonates with aromatic aldehydes and ketones, presumably by rearrangement of the initial a-hydroxy compounds. Further reports have appeared of the generation of metaphosphates by various methods. The synthesis of analogues 1 of famesyl pyrophosphate which incorporate photoactive esters has been reported both compounds are competitive inhibitors of farnesyl transferase. 

The Friedel Crafts (F C) reaction via activation of electrophiles functionalized by a nitrogen atom, such as imines, is undoubtedly the most practical and atom eco nomical approach to introduce a nitrogen substituted side chain to aromatic com pounds. The enantioselective version of the F C reaction of nitrogen substituted substrates, including imines, with electron rich aromatic compounds enables effi cient access to enantioenriched aryl methanamine derivatives [37[. Several excellent approaches to highly enantioselective F C reactions have been established using chiral phosphoric acid catalysts. 

Aminals, compounds having two amino groups bound to the same carbon atom, are represented in many medicinal agents having versatile therapeutic action, such as proteinase inhibitors and neurotensins. Antilla and coworkers developed an en antioselective synthesis of protected aminals from the amidation reaction of N Boc imines with a series of sulfonamides catalyzed by chiral phosphoric acids (Scheme 3.54a) [111]. In this novel enantioselective transformation, phosphoric acid 9 exhibited excellent catalytic activity and enantioselectivity in addition to N Boc aromatic imines. The enantioenriched aminal products were stable upon storage neither decomposition nor racemization was observed in solution over several days. The same research group reported the enantioselective amidation reaction of N Boc aromatic imines with phthalimide or its derivatives (Scheme 3.54b) [112]. 

Addition of aliphatic hydrocarbons to ethylenic compounds occurs under the influence of catalysts such as sulfuric acid, phosphoric acid, and aluminum chloride.1 For instance, isobutane and propene afford the three isomeric heptanes. This reaction is not of particular importance in laboratory practice. However, addition of aromatic compounds to olefins is often a practicable method of alkylation.2 Thus ethylbenzene is formed from ethylene and benzene under the influence of aluminum chloride or when the hydrocarbon mixture is passed over a silica-alumina catalyst and Brochet3 obtained 2-phenyl-hexane from benzene and 1-hexene. The C-C bond is always formed to the doubly bonded carbon atom carrying the smaller number of hydrogen atoms benzene and propene, for instance, give cumene, which is important as intermediate in the preparation of phenol. Corson and Ipatieff4 report that benzene reacts especially readily with cyclohexene, yielding cyclohexylbenzene ... 

Although the original Blanc procedure using paraformaldehyde (sometimes called tri-oxymethylene) and fused and pulverized zinc chloride is followed in many preparations, this reaction has been modified by using either 85% phosphoric acid as catalyst or ZnCh as catalyst but with AlCl or NiCl as cocatalyst. In addition, 40% formaldehyde has been used for this reaction instead of paraformaldehyde. Bromomethylation of aromatic compounds could be considered another modification. ... 

Catalytic AFC reactions of indoles have attracted considerable attention, and there has been significant progress in this area since 2009. Catalytic AFC reactions of aromatic and heteroaromatic compounds with a-imino esters provide a direct approach to optically pure aryl and heteroaryl glycines. In 2009, You and co-workers realized the AFC reaction of indoles with ethyl glyoxylate imine with 10 mol% of chiral phosphoric acid (S)-13b, affording (3-indolyl)glycine derivatives 28 in excellent yields (85-93%) with up to 87% ee (Scheme 6.11). ... 

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