Phosphonium salt synthesis

In the phosphonium salt synthesis, the addition reaction of tertiary phosphines to activated alkenes has been reported (Scheme 3). PPh3 is added to electron-deficient alkenes such as enones or enals at the p-position in the presence of acids.4 The reaction of styrenes with phosphine has recently been reported by Okuma, which gave Markovnikov adducts.5 Although no catalyzed reactions of... 

Before examining the reaction of deactivated alkenes, the phosphonium salt synthesis was applied to 1,3-dienes.21 When ( )-6-phenyl-l,3-hexadiene was treated with equimolar amounts of PPh3 and CF3S03H in the presence of RhH(PPh3)4 (2.5 mol%) in THF at 0 °C for 3 h, ( )-(6-phenyl-3-hexenyl)triphenylphosphonium salt was obtained in 89% yield after anion exchange with LiPF6 and recrystallization (Scheme 16). The addition of phosphine and hydrogen occurred at the 1- and 2-carbon atoms of the 1,3-diene, respectively. The reaction of (7)-1,3-dienes was then performed for comparison. 

F. Chretien, B. R. Castro, and B. Gross, ATDP Salts 22. A novel and efficient method for the preparation of glycosyl azides via alkoxy-tris[dimethylamino]-phosphonium salts. Synthesis (1979) 937-939. 

In the BASF synthesis, a Wittig reaction between two moles of phosphonium salt (vitamin A intermediate (24)) and C q dialdehyde (48) is the important synthetic step (9,28,29). Thermal isomerization affords all /ra/ j -P-carotene (Fig. 11). In an alternative preparation by Roche, vitamin A process streams can be used and in this scheme, retinol is carefully oxidized to retinal, and a second portion is converted to the C2Q phosphonium salt (49). These two halves are united using standard Wittig chemistry (8) (Fig. 12). 

The reaction of appropriate 1,3-diketones (302) with hydroxylamine hydrochloride in pyridine (79MI41601) has been reported to result in a regiospecific synthesis of 3-alkyl-5-arylisoxazoles, as has the reaction of an a -bromoenone (307) with hydroxylamine hydrochloride in ethanol in the presence of potassium carbonate (81H(16)145). Regiospecific syntheses of 5-alkyl-3-phenylisoxazoles also result from the reaction of an a-bromoenone (307) with hydroxylamine in the presence of sodium ethoxide (81H(16)145). 3-Aryl-5-methylisoxazoles were prepared from phosphonium salts (304) and hydroxylamine (80CB2852). 

Phosphonium hexafluorophosphate, benzotriazolyl-N-hydroxytris(dimethylamino)-in peptide synthesis, 5, 728 Phosphonium salts chromene synthesis from, 3, 753 reactions, 1, 531 Phosphonium salts, vinyl-in pyrrole synthesis, 4, 343 Phosphonium ylides in heterocyclic synthesis, 5, 165 Phosphoramide, triethylene-as pharmaceutical, 1, 157 Phosphoramide, triethylenethio-as pharmaceutical, 1, 157 Phosphorane, pentaphenyl-synthesis, 1, 532 Phosphoranes, 1, 527-537 Berry pseudorotation, 1, 529 bonding, 1, 528... 

A one-pot synthesis of alkyl perfluoroalkyl ketones has been developed. Phosphoranes, generated in situ, are acylated with a perfluoroacyl anhydnde, and the resultmg phosphonium salts are hydrolyzed with alkali [4S (equation 48) Hydrolysis of a carbon-sulfur bond in 2-chloro-2,4,4-trifluoro-1,3-dithietane-S-trioxide, which can be obtained from 2,2,4,4-tetrachloro-l,3-dithietane by fluor-mation with antimony trifluoride followed by selective oxidations, opens the nng to produce 2-chloro-1,1,2-trifluorodimethyl sulfone [49] (equation 49)... 

Another modification of the Hantzsch thiazole synthesis afforded C-4 thiazolylmethyl phosphonium salts (49). These ylids could then undergo Wittig condensations to furnish a wide variety of 2,4-disubstituted thiazoles <96TL983>. 

The jS-oxido-ylides synthesis of trisubstituted olefins has also been applied to the synthesis of farnesol (127). The phosphonium salt (123) with the aldehyde (124) and formaldehyde gave the hydroxy farnesol derivative (125) which was transformed into farnesol (127) and into (126), a position isomer of Cj juvenile hormone. 

Benzylphosphonates have been used in the synthesis of polymethoxy-stilbenes and of (174) and (175). The hydrocarbon (175) obtained in this way was much easier to purify than that prepared using the bis-phosphonium salt. 

The reaction of dipyridyl disulphide with triphenylphosphine to give the stable phosphonium salt (51) has been used in new methods of phosphorylation (reaction A), in peptide synthesis (reaction B), and in the formation of active esters of cx-amino-acids (reaction C). These reactions appear to have synthetic potential. 

This is an extremely useful reaction for the synthesis of alkenes. It involves the addition of a phosphonium ylid, e.g. (136), also known as a phosphorane, to the carbonyl group of an aldehyde or ketone the ylid is indeed a carbanion having an adjacent hetero atom. Such species are generated by the reaction of an alkyl halide, RR CHX (137), on a trialkyl- or triaryl-phosphine (138)—very often Ph3P—to yield a phosphonium salt (139), followed by abstraction of a proton from it by a very strong base, e.g. PhLi ... 

Elucidation of the physiological role of arachidonic acid 13 and other polyunsaturated fatty acids, particularly the role of all Z-4,7,10,13,16,19-decosahexaenoic acid 14, found in brain, required the corresponding stable-isotope labelled material1011. The deuteriated phosphonium salt 15, the key intermediate used in the synthesis of title compound 16 (equation 8), has been prepared in 19% overall yield12 starting with ethanol-D6 (equation 7). 

K. Manabe, Synthesis of Nobel Chiral Quaternary Phosphonium Salts with a Multiple Hydrogen-Bonding Site, and Their Application to Asymmetric Phase-Transfer Alkylation , Tetrahedron 1998, 54, 14465-14476. 

Synthesis of Phosphonium Salts by Metal-Catalyzed Addition Reaction... 

Phosphonium salts can be synthesized from unsaturated compounds by addition of a triarylphosphine and an acid in the presence of a palladium or rhodium catalyst. Transition metal catalysis turned out to be effective for the synthesis of organophosphorous compounds. 

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