Aryl-phosphorus coupling

The conversion of aryl iodides to aryl phosphonates, useful precursors to aryl phos-phonic acids, has been conducted in a Teflon autoclave by Villemin and colleagues [132]. A domestic MW oven was used for these experiments and the reaction times using classic heating were effectively reduced from 10 h to 4-22 min. The reactiv- 

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Transition metal-catalyzed C—P cross-coupling affords powaful tool for the preparation of aryl phosphorus compounds [198]. The scope of the phosphorus-based nucleophiles used in crosscoupling with aryl electrophiles in the presence of transition metal (Pd-, Cu-, and Ni-based) catalysts is very broad. Figure 20.5 summarizes the common phosphoms nucleophiles used for crosscoupling reactions (for mechanism, see Scheme 20.2). 

But we have a puzzle here since rotation around the aryl-CHP2 bond should be relatively unhindered, why does CP not couple to both aP and bP We will return to this question when we discuss the 2D phosphorus-phosphorus correlation experiment. 

The series of wide-bite-angle, bulky ligands derived from a cyclobutene scaffold gave Pd complexes (117) showing appreciable activity in the cross-coupling of reactive aryl bromides with trimethylsilylacetylene. A considerable shift of electron density to the phosphorus atoms, probably arising from alternative aromatic canonical structures, may account for the ligand properties.422... 

Coupling of Aryl and Vinyl Halides with Phosphorus(V) Reagents 386... 

Another spacer which was used to insulate the phosphorus atom from the electron-withdrawing effect of the perfluoroalkyl tail is the -0-(CH2) - spacer that contains an electron-donating oxygen atom directly attached to the aryl ring [25]. Fluorous derivatives of triphenylphosphine containing this ether spacer (13a-c) were prepared, though the lower coupling constant of cis-... 

Sulfonic acids are prone to reduction with iodine [7553-56-2] in the presence of triphenylphosphine [603-35-0] to produce the corresponding iodides. This type of reduction is also facile with alkyl sulfonates (16). Aromatic sulfonic acids may also be reduced electrochemicaUy to give the parent arene. However, sulfonic acids, when reduced with iodine and phosphorus [7723-14-0]y produce thiols (qv). Amination of sulfonates has also been reported, in which the carbon—sulfur bond is cleaved (17). Ortho-lithiation of sulfonic acid lithium salts has proven to be a useful technique for organic syntheses, but has litde commercial importance. Optically active sulfonates have been used in asymmetric syntheses to selectively O-alkylate alcohols and phenols, typically on a laboratory scale. Aromatic sulfonates are cleaved, ie, desulfonated, by uv radiation to give the parent aromatic compound and a coupling product of the aromatic compound, as shown, where Ar represents an aryl group (18). 

Trisphaeridine, [8]. The synthesis [9] of trisphaeridine (17) (Scheme 4) involved the known aryl boronic acid 18 and the sterically unencumbered o-bromophenylcaibamate 19 as coupling partners in the Suzuki reaction. The biaryl 20, thus obtained in customary good yield, underwent a Bischler-Napieralsky cyclisation with phosphorus oxychloride to afford the chlorophenanthridine 21. The latter on catalytic dechlorination furnished 17. 

The 2- and 3-phospholenes are prepared by the McCormack reaction and are good candidates as starting materials for the preparation of five-and six-membered phosphorus heterocycles [25-27]. From l-methoxy-3-methyl-2-phospholene 64 or l-methoxy-2,3-diacetoxy-3-methylphospholane 67, l-aryoxy-3-methyl-2-phospholenes 66a-c (Scheme 19), or l-aryoxy-2,3-diacetoxy-3-methylphospholane 69 (Scheme 20) with a substituted phenyl group at phosphorus, or l-aryl-3-methyl-2-phospholenes 71a-g (Scheme 21) are prepared by a substitution reaction and/or a Grignard coupling reaction [28,29]. 

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