Silver phosphonate salt

Toste has demonstrated the hydroalkoxycarbonylation of P-allenyl carboxylic acid derivatives catalyzed by a mixture of a chiral, enantiomerically pure bis(gold) complex and a chiral, enantiomerically enriched silver phosphonate salt [107]. As an example, treatment of 6-methyl-4,5-heptadienoic acid with a catalytic mixture of [(S)-binapj (AuC1)2 and Ag-(J )-67 formed the yluctone 83 in 88% yield with 82% ee (Eq. (12.43)) [107]. 

The phenylselenenyl chloride/silver tetrafluoroborate induced purino-selenenylation of the unsaturated phosphonate derivatives 50 gives the adducts 52 in modest yields but with a good control of the stereoselectivity (>80% de). This stereoselectivity is in good agreement with preferential formation of the seleniranium salt 51 which undergoes stereoselective opening by a purine base to give the adducts 5296. 

SULFICYLBIS (METHANE) (67-68-5) CjHjOS (CH3)2S0 Combustible liquid [explosion limits in air (vol %) 2.6 to 63.0 flashpoint 203°F/95°C oc autoignition temp 419°F/215°C Fire Rating 2]. Violent or explosive reaction with strong oxidizers, acryl halides, aryl halides and related compounds, alkali metals p-bromobenzoyl acetanilide, boron compounds, especially hydrides iodine pentafluoride, magnesium perchlorate, methyl bromide, perchloric acid, periodic acid, silver fluoride, sodium hydride, potassium permanganate. Forms powerfully explosive mixtures with metal salts of oxoacids [iron(III)nitrate, phosphonic acid, sodium perchlorate]. On small fires, use dry chemicals or COj extinguishers. 

Although it might be expected that reactions which employed triarylmethyl halides would occur very readily, such reactions are rendered potentially more complex by the known nature of the halides and their propensity for involvement in free radical reactions. Whereas normal alkylation proceeds between sodium diethyl phosphite and diphenyl-methyl halides, success, or otherwise, in the use of the triphenylmethyl halides depends to some extent on the individual halide and on the metal in the phosphite salt. Thus, in an early study (in 1939), Arbuzov found that in reactions between silver dialkyl phosphites and triphenylmethyl bromide, dialkyl triphenylmethylphosphonates were indeed formed, but the use of the corresponding alkyl chloride provided the phosphite triester instead (metal dialkyl phosphites possess ambident anions ). A later study confirmed the behaviour of the silver salts towards the chloride, but also showed that, whereas dialkyl phophites with primary alkyl groups yielded phosphonic diesters (as had already been found), those with secondary alkyl groups afforded phosphite triesters moreover, the presence and nature of aromatic substituents were also able to control the course of the reaction. Reactions which involve triarylmethyl halides and sodium dialkyl phosphites may well be of a free radical nature since repeated studies have demonstrated the forma-... 

Two promising observations consist of the activation of the interaction of haloketones and phosphorus(III) esters towards phosphonate formation by the presence of silver salts and also a two-step process in which a silyl ether ArC(OSiMe3)=CHR is first treated with PhI0-BF3 Et20 at -40 °C, and the resultant complex is then treated with a trialkyl phosphite, again at -40 °C, when the products are the expected 0x0 phosphonic diesters, (EtO)2P(0)CHRCOAr ... 

Diesters of (diazomethyl)phosphonic acid are fairly acidic and metal salts are readily available the lithium salts from these and the esters of other comparable acids are normally prepared in situ through reaction with BuLi, whilst silver salts are normally obtainable from Ag20 . The salts so obtainable are reactive to alkyl halides to give the diesters of homologous (l-diazoalkyl)phosphonic acids ... 

A further displacement of practical utility is that of halogen in phosphonic and phos-phinic chlorides by carboxylate ions (with silver or thallium salts, for example) to give mixed anhydrides, e.g. 581 and 582. Such anhydride formation provides a system particularly reactive at the carbonyl group towards nucleophiles, and thus preliminary activation of the carboxyl group by the diphenylphosphinoyl group becomes useful in amide or peptide formation ... 

Silver-catalyzed 1,2-arylphosphorylation of activated alkynes has been developed for assembling 3-phosphonated coumarins (Scheme 9.37) [43]. This method employs a cheap and nontoxic silver salt to catalyze the domino C-P and C-C bond formation of alkynoates for the first time. 

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