Pschorr reactions synthesis

Pschorr reaction. Synthesis of phenanthrene derivatives from diazotized a-aryl-omicron-amino-cinnamic acids by intramolecular arylation. 

Protoporphyrin-IX, N-methyl-, 4, 396 Protoporphyrins, 4, 382 photooxygenation, 4, 402 Prototropic tautomerism polyheteroatom six-membered rings, 3, 1055 Prozapine properties, 7, 545 Pschorr reaction carbolines from, 4, 523 dibenzazepines from, 7, 533 dibenzothiophenes from, 4, 107 phenanthridines from, 2, 433 Pseudilin, pentabromo-synthesis, 1, 449 Pseudoazulene synthesis, 4, 526 Pseudobases in synthesis reviews, 1, 62 Pseudocyanines, 2, 331 Pseudothiohydantoin synthesis, 6, 296 Pseudouracil structure, 3, 68 Pseudoyangonin IR spectra, 3, 596 Pseudoyohimbine synthesis, 2, 271 Psicofuranine biological activity, 5, 603 as pharmaceutical, 1, 153, 160... 

The Pschorr reaction, originally applied to the synthesis of phen-anthrene and its derivatives,has been adapted to the formation of new heterocyclic systems.In its original form, it consisted of treating a diazonium salt with copper powder in acid solution in this way, rans-o-amino-a-phenylcinnamic acid was converted into phen-anthrene-9-carboxylic acid, Eq. (20). Variants of the reaction include cyclizations such as that in Eq. (21). The reaction may be horaolytic... 

The Pschorr reaction is a method of synthesis of phenanthrenes from diazotized Z-2-aminostilbenes. A traditional procedure involves heating with a copper catalyst. Improved yields are often observed, however, if the diazonium ion is treated with iodide ion. Suggest a mechanism for the iodide-catalyzed reaction. 

Intramolecular radical arylations are found to work quite well, however, e.g. the Pschorr reaction this involves the thermal decomposition of diazonium salts, e.g. (112), in the presence of copper powder as catalyst, and is used in the synthesis of phenathrenes such... 

Pschorr s synthesis of phenanthrene (1893) in five steps with the essential dediazoniation and ring closure of 2-diazonio-a-phenylcinnamic acid giving, on addition of copper powder, phenanthrene-9-carboxylic acid, is today still the highest yielding one of all the reactions discussed in this section, Pschorr was able to get 93% yield, and today electrochemically induced Pschorr and related reactions141 give almost quantitative yields in several cases. 

Cohare and co-workers reported that aristolactam BU (22) was prepared, following Kupchen s method, by Perkin condensation of 6-bromo-3,4-di-methoxy phenyl acetic acid (119) and o-nitrobenzaldehyde (120) (Scheme 14). The 2-bromo-4,5-dimethoxy-2 -nitro-ds-stilbene-a-carboxylic acid (121) was obtained. The nitro group of 121 was reduced with ferrous sulfate and ammonium hydroxide, and the resulting 2-bromo-4,5-dimethoxy-2 -amino-cw-stilbene-a-carboxylic acid (122) without purification was submitted to the Pschorr phenanthrene synthesis to yield l-bromo-3,4-dimethoxyphen-anthrene-lO-carboxylic acid (123). The phenanthrylamine 124 was prepared from 123 via a Schmidt reaction, and, by treatment with n-butyllithium and CO2, 124, afforded 22 (42). 

The Pschorr reaction is valuable in the synthesis of carbolines. The 3-aminopyridine (165) gives the a-carboline (166 78%) under free-radical conditions, but the aniline... 

Coumarin synthesis. The Pschorr coumarin synthesis involves the reaction of phenols with -keto esters in the presence of a condensing agent (usually sulfuric acid). In a synthesis of the coumarin mold metabolite aflatoxin M, (3), Biichi and Weinreb found that the usual conditions could not be employed because the phenol (I) is exceptionally sensitive to acidic reagents. However, they effected the desired condensation of... 

A 2-aminodiaryl ether (79.2, X = O) is cyclized to the furopyridine (79.3, X = O) by using the Pschorr reaction—thermolysis ofa mixture of the diazonium salt and copper powder. The use of heterocyclic diazonium salts in organic synthesis has been reviewed [2980]. Rhodium(II) acetate catalyses the room-temperature cyclization of a-diazo-jS-oxo esters (79.4) by carbenoid insertion into a benzenoid C—H bond. 

As a step in the synthesis of a higher homologue of the antibiotic thienamycin, the closure of the pyridine ring is effected by warming the diazo ester (793) with rhodium(II) acetate (review of rhodium-catalysed reactions [3928]) the product (79.6, R = H) is more easily isolated and purified as its O-tosyl derivative (79.6, R = Ts). Intramolecular homolytk cyclization (the Pschorr reaction) of the diazonium salt of N-methylbenzanilide gives moderate yields which are comparable with those given by the pyrolytic cyclization of the 2-iodo analogue (see Chapter 90, Section II.2 [2303]). 

Some years ago a general synthetic method 52) for the morphinan-dienone-type alkaloids was discovered by modifying the Pschorr reaction which had been used widely for the synthesis of the aporphine alkaloids and this method was applied to a synthesis of the homo-morphinandienone-type compounds. 

For an excellent overview of Pschorr phenanthrene synthesis see D.F. DeTar, Organic Reactions, 9, (1957), 409. 

C1SH 2 mol wt 228.29. C 94.70%, H 5.30%. Synthesis by a Pschorr reaction from diazotized -(2-naphthyl)-2-amino-cinnamic acid Cook, J. Chem. Soc. 193t, 2524. From di-phenylmethylsoccinic anhydride Heweit, J. Chem. Soe. 

One of the most important fields of application of the Pschorr reaction is the synthesis of isoquinoline alkaloids. The syntheses of thalicsimidine [72] (Scheme 46) and aporphine [73] are typical examples. 

The Pschorr reaction was described in connection with the synthesis of the papaverine (3) derivatives (350, 351). The synthesis of petaline (5b) was accomplished (352, 353). Escholamine (4a) and takatonine (4c) were synthesized by a modified Pomeranz-Fritsch reaction (354). The phenolic oxidation of (f )-(-)-N-methylcoclaurine (7c) and (S)-(+)-reticuline (7f) with peroxidase proved to be a failure (355). The oxidation of reticuline with ferricyanide yielded isoboldine (24c) and pallidine (43b) and the byproducts vanillin and thalifoline (2c) (355). A new synthesis of 3-oxo-papaverine was developed (356), and the Eschweiler-Clark method for the synthesis of codamine (7r) was modified (357). Oxidation of reticuline (7f) by enzymatic systems from homogenized P. rhoeas in the presence of hydrogen peroxide gave ( )-/3-hydroxyreticuline (10) (358). 

Four major reactions (Pschorr, phenol oxidative coupling, photocyclization, and benzyne-mediated synthesis) continue to play key roles in the total synthesis of aporphine and proaporphine alkaloids. Coninnine (96) was synthesized according to Scheme 5, employing the Pschorr reaction as the key step. An... 

Closely related arylation to Pschorr reaction is the Gatterman synthesis of biaryls (II) which involves the coupling reaction of two aryldiazonium salts (III) by the influence of copper or copper(I) salts [97,98], Scheme 24. 

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