C. Muthiah

Direct synthesis of α-substituted phosphonates

The a-substituted phosphonates (OCH2CMe2CH2O)P(O)CH(X)(Ar) [X=Cl, OMe, NMe2 and OSiMe3], useful precursors for Horner–Wadsworth–Emmons reactions, are readily prepared by treating (OCH2CMe2CH2O)PX with an aromatic aldehyde. In the reaction of (OCH2CMe2CH2O)PCl with furfuraldehyde and cinnamaldehyde, the 5-chlorofurfurylphosphonate (OCH2CMe2CH2O)P(O)CH2(5-Cl-C4H2O) and the g-chlorophosphonate (OCH2CMe2CH2O)P(O)CH CH-CH(Cl)Ph, respectively, are formed in good yields.

New phosphoranes with five- and seven-membered rings: influence of the nature of the substituents on hydrogen bonding

Abstract Several pentacoordinated phosphoranes with a primary amino substituent have been synthesized by oxidative addition reactions on a cyclic phosphite. X-ray structures of three of these, i.e. (C6H11NH)P(2,2′-O-C6H4-C6H4-O)(1,2-O2C6Cl4) (6), (C6H11NH)P(9,10-O2C14H8)(1,2-O2C6H4) (7) and (MeNH)P(2,2′-O-C6H4-C6H4-O)(1,2-O2C6H4) (8) have been determined. While 6 does not show hydrogen bonding interactions involving the NH proton, compound 7 is a weak dimer with hydrogen bonding interactions between the NH proton and the apical oxygen of the catecholate ring. By contrast in 3, although hydrogen bonding again involves the NH proton and apical oxygen of the five-membered catecholate ring, a polymeric chain structure is formed.

An easy access to trisubstituted vinyl chlorides and improved synthesis of chloro/bromostilbenes

The α-chlorophosphonates (OCH2CMe2CH2O)P(O)CHCl-C6H4-4-R [R=H (4), Me (5), OMe (6)], which are now readily accessible, react with ketones R′C(O)R″ in the presence of NaH (without recourse to the more expensive t-BuLi) to afford trisubstituted vinyl halides R′C(R″)=CCl(C6H4-4-R) in good yields. The corresponding α-bromophosphonates [R=H (7), Me (8)] failed to react with ketones and gave the symmetrical acetylenes 4-R-C6H4-CC-C6H4-4-R as isolable products in low yield. We have found that K2CO3 in refluxing xylene is a good base for the synthesis of chlorostilbenes; using this base the bromostilbenes ArCH=CBr(C6H4-4-R) can be prepared in significantly higher yields than by using NaH. The stereochemistry of two of the trisubstituted vinyl chlorides is unambiguously proven by X-ray structure determination. Thus for (Cl)PhC=CPh(Me), the isomer with the upfield NMR shift for the CH3 protons and for (Cl)PhC=C(Ph)(C6H4-4-Me), the isomer with the downfield NMR shift for the -C6H4-4-CH3 protons have Z stereochemistry.

Synthesis, reactivity and structures of spirocyclic products derived from octachlorocyclotetraphosphazene: comparison with spirocyclic cyclotriphosphazenes and linear phosphazenes

The reaction of N4P4Cl8 1 with the difunctional reagents 2,2′-methylenebis(4,6-di-tert-butylphenol) (as its disodium salt) and N,N′-diisopropylpropane-1,3-diamine gave the spirocyclic products 2,2-N4P4{[O-4,6-(t-Bu)2C6H2]2CH2}Cl6 4 and 2,2-N4P4[N(i-Pr)CH2CH2CH2N(i-Pr)]Cl6 5. Further reaction of 1 with 2 mol equivalents of N,N′-diisopropylpropane-1,3-diamine afforded the novel dispiro derivative 2,2,6,6-N4P4[N(i-Pr)CH2CH2CH2N(i-Pr)]2Cl4 6. Whereas the analogous reaction of N3P3Cl6 2 with the above diamine gave the monospiro derivative 2,2-N3P3[N(i-Pr)CH2CH2CH2N(i-Pr)]Cl4 7 readily, the reaction of 2 with the diols CH2[4,6-(t-Bu)2C6H2OH]2 or CH2(4-Me-6-t-BuC6H2OH)2 is sluggish. In the case of the latter diol, a product formulated as N3P3[O-4-Me-6-t-BuC6H2-4-Me-6-t-BuC6H2OH]Cl5 9 was identified (31P NMR). The linear phosphazene Cl2P(O)NPCl3 3, by contrast, reacted with CH2(4-Me-6-t-Bu-C6H2OH)2 and Et3N to give the cyclic product Cl2P(O)NP[(O-4-Me-6-t-BuC6H2)2CH2]Cl 8. Reaction of the spirocycle 5 with an excess of MeNH2/Et3N afforded the new bicyclic phosphazene containing a spirocyclic ring N4P4[N(i-Pr)CH2CH2CH2N(i-Pr)](NHMe)4(NMe) as a crystalline solid. The crystal structures of 4·0.5C4H8Cl2 and 5–8 have been determined.

2,2'-Biphenyl (cyclohexylamino)phosphonate: a hydrogen-bonded dimer

The structure of the title compound, C 18 H 20 NO 3 P, reveals a hydrogen-bonding interaction between the NH group and the phosphoryl-O atom, resulting in a dimer; no interaction of the O atoms of the seven-membered 1,3,2-dioxaphosphepine ring with the NH proton is found.

Oxidative addition reactions of cyclic aryloxy-, amino- and chloro-phosphites and arsenites

Reaction of cyclic phosphites with 1,2-diketones and with diol/N-chlorodiisopropylamine has been studied. A large number of penta- and hexacoordinated phosphorus derivatives with varying ring sizes have been synthesized and structurally characterized. The reactivity of phosphites is compared with that of arsenites and pentacoordinated phosphoranes. Several phosphonates that are important as synthetic reagents have been prepared by reacting cyclic phosphites with aldehydes.