Heterocycles phosphorus, from

As with five-membered heterocycles, phosphorus pentasulfide may replace a ring oxygen atom by sulfur, or it may effect replacement in an acyclic precursor and then bring about cyclization. Thus isochroman-l-one (99) is converted into thioisochroman-l-thione (100) under the same conditions a 3-arylisocoumarin( 101) produces a 3-ary 1-1-thioisocoumarin (102) only, with no replacement of the ring oxygen atom.122 A typical example of thiation, followed by cyclization, is the formation of 2-alkyl- or 2-aryl-3,l-benzo-thiazine-4-thiones (103) from /V-acylanthranilic acid esters (104) by treatment with phosphorus pentasulfide in boiling xylene.122... 

Recent work in the chemistry of phosphorus heterocycles derived from a-hydroxyalkylphosphines and vinylphosphines, much of which has appeared in the Russian language literature, is covered by B. A. Arbuzov and G. N. Nikonov (Kazan, Russia). 

The second class of benzo-fused heterocycles accessible from benzofuroxans are benzimidazole oxides. In this case only one carbon from the co-reactant is incorporated in the product. With primary nitroalkanes 2-substituted l-hydroxybenzimidazole-3-oxides (46) are formed via displacement of nitrite, and / -sulfones behave similarly. The nitrile group of a-cyanoacetamides is likewise eliminated to alford 2-amide derivatives (46 R = CONRjX and the corresponding esters are formed in addition to the expected quinoxaline dioxides from acetoacetate esters. Under similar conditions secondary nitroalkyl compounds afford 2,2-disubstituted 2//-benzimidazole-1,3-dioxides (47). Benzimidazoles can also result from reaction of benzofuroxans with phosphorus ylides <86T3631>, nitrones (85H(23)1625>, and diazo compounds <75TL3577>. 

The nature of the aryl substituent attached to phosphorus has a subtle influence on the ring size of the organophosphorus-sulfur heterocycle obtained from the reactions of ArPCl2 (Ar = aryl) and a source of sulfide. The six-membered ring cyclo-(Mes PS)3 is formed from treatment of Mes PCl2 with lithium sulfide the P3S3 ring adopts a chair conformation with the sulfur atoms... 

A single example of a phosphorus-containing heterocycle made from a thiourea is the 1,3,4-diazaphospholane (97) prepared in 80% yield via treatment of 96 with phosphorus trichloride.215... 

Heterocyclic phosphorus ylides (e.g., 114, R = Me) containing an azepinedione nucleus have been prepared, although in low yield (13-26%), by flash vacuum pyrolysis (FVP) of the corresponding open-chain ylide precursor 113 (Equation 15) <2001TL141>. The authors noted, however, that the azepinediones were isolated from the inlet residue rather than from the cold trap after the pyrolysis tube. 

Carbonyls. Several papers have appeared this year from Issleib s group describing the synthesis of heterocyclic phosphorus compounds by acid-catalysed condensations of phosphines with carbonyl compounds. (Mercapto-alkyl)phenylphosphines (31) react with aldehydes or ketones to form 1,3-thiaphospholans or 1,3-thiaphosphorinans. The intermediate compound (32) can be isolated from a similar reaction with phenylisothiocyanate and is converted into a thiaphospholan by intramolecular loss of hydrogen sulphide. 

The formation of ethers can also occur with cyclization and the synthesis of heterocyclic phosphorus compounds (Scheme 37). The reaction between the benzodioxaphosph(V)ole 241 and a Grignard reagent (R = alkyl or aryl) followed by a treatment of the product 242 with base affords the dihydrobenzodioxaphosph(V)orin 243 also available from catechol and bis(chloromethyl)phosphinic chloride. The hydrolysis of243 and cyclization of... 

The unusual phosphole ring C FejP was synthesized by Huttner and co-workers (Scheme 12). In terms of Wade s rules (b) is an arachno system which can be converted into a nido cluster, (c), upon decarbonylation. The latter can form directly in the photochemical reaction of (a) with alkynes. The hve-membered organometallic heterocycle (c) is planar (deviation < 0.07 A) indicating delocalized bonding (structure 39). Signihcant developments may be expected from this new class of compounds. New types of heterocyclic phosphorus ligands are continuing to be synthesized, e.g. a 1,3,5-triphosphabenzene derivative, l,l,3,3-tetrakis(dimethylamino)-4-r-butyl-U 3x 5A -tri-phosphabenzene (40). 

The importance of the substitution pattern on the phosphole in this reaction was obvious from continued studies <78JHC1319> that showed that a much higher order of reactivity and the formation of a quite different 1 2 adduct (82) could be experienced with phospholes of structure (80) and (81). Structure (82) also is novel in heterocyclic phosphorus chemistry and does not seem to have been approached by any other method (Equation (12)). 1-Phenylphosphole also reacts rapidly with the ester, but gave a mixture of products in low yield. One product is probably of the same type as (82) the other is tentatively assigned structure (83). All of these early results with acetylenedicarboxylate have been summarized in a review <81H(15)637>. In terms of mechanism, in every case it appears that the initial step is the action of the phosphorus atom as a typical nucleophilic phosphine in attacking on the triple bond (Equation (13)). Subsequent reactions involve attack on the ring carbons and on a second alkynic group, but details of these processes have not been fully established. 

This was the first approach used for the synthesis of a monocyclic phosphole, the pentaphenyl derivative, and stands as a landmark in heterocyclic phosphorus chemistry. In 1959, two laboratories reported the synthesis of this compound. In one synthesis, the dilithio derivative of tetra-phenylbutadiene was reacted with phenylphosphonous dichloride (Scheme 61) the reaction proceeded in excellent yield (84% <59JA3163,60JA5099 . Since the starting diene is easily prepared from diphenylethyne and lithium, it remains the best way to prepare this derivative, which has found use in many subsequent studies. In addition to the P-phenyl derivative, the P-benzyl compound was also reported (38% <6UA4406 . 

The phosphorylation of nitriles sometimes yields imidoyl chlorides 186,25evidenced by the isolation of the heterocyclic phosphorus compounds XLVII from the reaction of malonitrile and phosphorus penta-chloride... 

There are some reports on phosphorus heterocycles made from acyclic amino alcohols other than ephedrine. Most of these amino alcohols are easily... 

Because of the structural requirements of the bielectrophile, fully aromatized heterocycles are usually not readily available by this procedure. The dithiocarbamate (159) reacted with oxalyl chloride to give the substituted thiazolidine-4,5-dione (160) (see Chapter 4.19), and the same reagent reacted with iV-alkylbenzamidine (161) at 100-140 °C to give the 1 -alkyl-2-phenylimidazole-4,5-dione (162) (see Chapter 4.08). Iminochlorides of oxalic acid also react with iV,iV-disubstituted thioureas in this case the 2-dialkylaminothiazolidine-2,4-dione bis-imides are obtained. Thiobenzamide generally forms linear adducts, but 2-thiazolines will form under suitable conditions (70TL3781). Phenyliminooxalic acid dichloride, prepared from oxalic acid, phosphorus pentachloride and aniline in benzene, likewise yielded thiazolidine derivatives on reaction with thioureas (71KGS471). 

Phosphorus heterocyclic compounds, 1, 493-538 five-membered ring systems, 1, 513-523 nomenclature, 1, 496 six-membered ring systems, 1, 497-513 Photoaromatization oxirenes from, 7, 125-126 Photobleaching chromenes in, 3, 880 Photochemical reactions heterocyclic compound synthesis from, 5, 159 reviews, 1, 56 heterocyclic compounds reviews, 1, 71, 72... 

Ti -Cyclopentadienyl(triphenylphosphine)cobalt reacts with phosphites and forms complexes of 1-alkoxyphosphole oxides 251 (R = Me, Et, Ph) through a step involving (ri -cyclopentadienyl)(phosphite)cobalt (80JA4363). (ri -Cp)Co(PF3)2 reacts with hexafluorobut-2-yne and 252 is formed, which hydrolyzes into 253 (X = OH) [73JCS(CC)583 75JCS(D)197]. The five-member ring has the envelope conformation, in which the carbon atoms are coplanar, and the phosphorus atom deviates from this plane in the direction opposite to the cobalt atom. The heterocycle is a four-electron donor relative to the metal center. 

In much the same vein, reaction of the heterocycle, 145 (obtainable from phthalic acid and hydrazine), with phosphorus oxychloride gives the dichloride, 146. Double displacement of halogen by means of hydrazine leads to dihydralazine (147)... 

The representatives of this heterocyclic system were prepared by cyclodehydration of 5-acylaminotriazin-6-ones 616, obtained from 615, with phosphorus pentoxide to give the corresponding 3-phenyloxazolo[4,5-e]triazines 617 (87AJC977) (Scheme 127). 

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