Aryl phosphates coupling reactions

De Carolis, M., Protti, S., Fagnoni, M. and Albini, A. (2005) Metal-free cross-coupling reactions of aryl sulfonates and phosphates through photoheterolysis of aryl-oxygen bonds. Angewandte Chemie, International Edition, 44, 1232-1236. 

Chemiluminescence is the production of light from a chemical reaction. The emitted light is detected with either a luminometer or on photographic film. There are several substrates capable of producing these light emissions and luminol (5-amino-2, 3-dihydro-l, 4-phthalazinedione) and adamantyl 1,2-dioxetane aryl phosphate are two of the most popular.114,115 The former is used with horseradish peroxidase (HRP) coupled antibodies and the latter is used with alkaline phosphatase (AP)-coupled antibodies. Using an AP-cou-pled antibody and adamantyl 1, 2-dioxetane aryl phosphate, Bronstein et al.U5 were able to detect as little as 125 pg of protein in a Western blot. 

In place of the aryl halide or alkenyl halide, the corresponding phosphate or triflate have been employed for the above cross-coupling reaction (O Scheme 71) [102]. These substrates were easily prepared from the corresponding lactone. The reaction of alkenyl phosphate or triflate has frequently been employed in the synthesis of marine polycyclic ethers such as brevetoxin... 

Allyiic halides, alcohols, ethers, acetates, lactones, phosphates, epoxides, sulfides, sulfonium salts, se-lenides and ammonium salts undergo transition metal catalyzed coupling reactions with C(sp )—Li, —Mg, —B, —Al, —Sn, —Zt, —Cd and — Hg reagents. Table 1 summarizes the allyiic leaving groups, alkenyl and aryl metallic reagents, catalytically active metals and references and Table 2 the regio- and stereo-chemical aspects. 

In the absence of base-sensitive groups in both alkylboranes and organic halides, PdCljCdppf) and sodium hydroxide in THF-HjO works nicely (Table 31.3, procedure A). For functionalized alkylboranes and halides, powdered sodium methoxide suspended in THF (procedure B) accelerates the reaction. However procedure B is less effective for vinylic halides. A promising coupling is achieved employing either potassium carbonate (procedure C) or potassium phosphate (procedure D), both suspended in DMF at 50 °C. The results also reveal that coupling reaction is applicable to iodides and bromides of vinyl and aryl halides (Chart 31.1) [2]. 

Han has comprehensively reviewed the use of nickel catalysts for the Suzuki-Miyaura cross-coupling reaction/ and found that the nickel mediated process can tolerate a broad range of aryl electrophiles, for example, sulfamates, carbamates, carboxylates, ethers, carbonates, phosphoramides, phosphonium salts, phosphates, phenols, and a broad range of alkyl substrates including both secondary and primary alkyl iodides, bromides, and chlorides. Many of these electrophiles have been found to be incompatible with traditional palladium catalysed processes. 

Table 8.17 Palladium-catalyzed cross-coupling reactions of benzyl manganese halides and phosphate with aryl iodides.

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