172. A new reagent for the oxidation of acyloins to diketones

The compounds M(SOCPh),, (M = Pb, n = 2; M = Bi, n = 3) have been prepared by the reaction of M(OAc), or M(SPh), with a slight excess of PhCOSH in MeOH. The ligands PhCOS-, (c-C6Hl1),PCS2 and (c-C6HI,),PO solubilize Pb(SOCPh), in solvents in which it is otherwise poorly soluble. Neither Ph,P nor Ph,P increase the solubility of Pb(SOCPh), and none of the above five ligands enhance the solubility of very poorly soluble Bi(SOCPh),. Solubilization of the Pb(I1) compound is due in each case to a 1: 1 reaction as shown by the isolation of (Ph,As)(SOCPh),] (1) and Pb(SOCPh),(S,CP(c-C6Hll 1, ) (2), and by a multi-NMR (,'P, ,07pb) study of the system Pb(S0CPh) : (c-C6Hl ,),PO (in which unidentified more ligand-rich species are also formed). 1 and 2 have been characterized by multi-nuclear magnetic resonance spectroscopy (I3c, ,IP, ,07pb, as appropriate) and by single crystal X-ray diffractometry techniques at -50°C. The compound l.CH,Cl, (= 1') crystallizes in the triclinic space group P i with Z = 2. The c stal data for 1' are a = 13.395 (4) (3)) g cM3, RF = 0.034, R,, = 0.029. The (c-C6Hl1),PCS, ligand binds in an anisobidentate manner and the primary coordination geometry around Pb in the neutra) molecule is trigonal pyramidal, the primary Pb-S distances in the PbS, kernel being 2.626(2), 2.755(2), and 2.885(2) A. The weakly bound sulfur of the (c-C6H,,),PCS, acts as a bridge, again producing a centrosymmetric dimer. In addition to the two weak inLeractions to sulfur

“…'07pb NMR chemical shifts found for mixtures of (Ph,As) [Pb(SPh),] and excess PhCOSH or (PhCOS), show that the [Pb(SOCPh),]-anion is also being formed according to reactions [5] and [6].…”

Section: Addition Of Donor Ligandsmentioning

confidence: 99%

“…For reaction [5] in CHC1, S,,(Av,,,) = 1414 (~1 4 0 Hz), while for reaction [6] in Me,CO, SPb(AvIn) = 1466 ( = l o Hz).…”

Section: Addition Of Donor Ligandsmentioning

confidence: 99%

Thiobenzoates of lead (II) and bismuth (III). The crystal and molecular structures of (AsPh₄) [Pb(SOCPh)₃] and Pb(SOCPh)₂(S₂CP{c-C₆H₁₁}₃)

Burnett¹,

Dean²,

Vittal³

1994

“…2.3-dimercapto-I-propanol (BAL). sodium 2.3-tlimcrcapto-I-propancsulfonatc (DMPS), bis(2-mercaptocthyl) cthcr or sulfide (all from Aldrich Chemical Co.), (21). tin(l1) acetate (22).…”

Section: Mrrrerict1rmentioning

confidence: 99%

A preparative and multinuclear nuclear magnetic resonance spectroscopic study of As(SPh)_x(SePh)_3−x(x = 0−3), Sb(SPh)_x(SePh)_3−x (x = 0−3), Bi(SPh)₃, Bi(SePh)₃, [Sn(SPh)_x(SePh)_3−x]⁻(x = 0−3), Pb(SePh)₃⁻, and Pb(SPh)₃⁻ and some related thiolatoplumbates(II)

Arsenault¹,

Dean²

1983

. Can. J. Chcm. 61. 1516Chcm. 61. (1983. The phenyl sclcnolatcs of tin(ll), Icad(l1). arscnic(lll), antirnony(lll), and bismuth(l1l). M(ScPh),, (M = Sn(ll) or Pb(ll), rr = 2; M = As(ll1). Sb(ll1). or Bi(lll), rr = 3). have been synthcsizccl by acid-base reaction of the appropriate metal acetate (for M = Sn(ll) or Pb(ll)) or thiophcnolatc (for all five clcmcnts) with PhScH. and characterized by clcrncntal analysis and, for the Group V elcmcnts, 77Sc and I3C nnir spectroscopy.M(SPh), and M(ScPh): (M = Sn(l1) or Pb(ll)) arc poorly solublc in McOH but dissolve in the presence of an equimolar or greater amount of P h S or P h S c . The solublc st;unnatc(ll) con~plcxcs arc triligatccl as shown by the slow exchange I1"Sn and, where appropriate. 7 7~c nmr spcctra of the series [Sn(SPh),(ScPh), , I (.r = 0-3) mcasurcd for the supernatant liquor of mixtures in which {Sn(EPh)l),,,,,,l/Pl~E -,,,,;,I > I . The corresponding plumbatc(ll) complcxcs arc pr-obably triligatcd also, but are labile on the nmr timcscalc; the parent complexes P b ( E P h ) havc bccn chmctcrizcd in solution by "I7pb and I3C (E = S and Sc) and 7 7~c (E = Sc) nmr spectroscopy. For both Pb(l1) and Sn(ll), the orclcr of chcmical shifts in the rnctal nmr spcctra is G(MSc3) > 6(MS,). The metal nmr spcctra of the mixturcs M(ScPh),:PhSc :PhS = 1 : 2 : 4 (M = Sn(ll) or Pb(ll)) show that the coordination of P h S c occurs in prcfcrcncc to coordination of P h S fo~. both tin(l1) and Icatl(l1).Thiolatoplurnbatcs(l1) might bc formed during somc antidotal treatments for lead poisoning, so "fingerprint" 2 " 7~b nmr spcctra havc bccn mcasurcd for a rangc of model s o l~~b l c spccics formed in Pb(SR),-(cxccss)RS mixturcs in McOH, including somc mixturcs containing newly synthcsizcd and characterized lead thiolatcs derived from dithiolatc unions. For RS-= MeS-, E t S . PhS-, C h H l l S -(for which "Pb(SR)Z" has bccn shown to bc Pb(SC,Hl1)(OAc)), S ( C H Z ) , S / 2 , -SCH,CHSMc/2. and -SCH,CHS C H~O H ' , 61.1, (from PbMc, in toluene as rcfcrcncc) falls in the conlparativcly short rangc 25 18-2999 pprn.The redistribution of ligands bctwccn M(SPh)> and M(ScPh), in chloroform to give cquilibsium mixtures of M(SPh),(SePh),..., occurs slowly on the preparative timcscalc for M = As, rapidly on the prcp~u.ativc timcscalc but slowly on the "C and 77Sc nmr timcscales for M = Sb, and rapidly on the ' C and 77Sc 111iir tinlcscalcs for M = Bi. Thus 13C and, where appropriate, 7 7~c nnlr data arc reported for M(SPh),(ScPh),+, (M = As or Sb) and Bi(EPh)> ( E = S or Sc). In addition, it has been possible, using I3C nmr assessment of spccics distribution in the systems Sb(SPh),-As(ScPh) and Bi(SPh)3-As(ScPh),, to dcducc that for the trivalent Group V clemcnts the ordcr of prcfcrcncc for PhSc-over PhS-as ligands is Bi > Sb > As.Trends in the I3C nmr data for M ( s P h ) . , ( s~P h )~ , (M = As or Sb) and 77Sc nnlr data for a rangc of metal complcxcs of PhSchavc been discussed. The sclcniurn chemical shifts arc influcnccd primarily by the acceptor atom and asc in the ordcr Cd(ll) ...

“…Attempts to hydrolyze the ester grouping in (VII, K = Me) were abortive, however, since the ketol underwent air-oxidation (17) and yielded no tractable product. (VII, K = Me) was converted by bismuth oxide (18) to the non-crystalline a-diketone characterized as the crystalline quinoxaline derivative (VIII).…”

Section: Hooc )mentioning

confidence: 99%

Terpenoids: V. Senegenin: Functional Groups and Part Structure

Dugan¹,

Mayo²,

Starratt³

1964

Senegenin, the sapogenin from Polygala senega has been shown to contain chlorine; it has the empirical formula C30H4506Cl. The oxygen atoms, contrary to earlier work, are contained in two carboxyl groups and two secondary hydroxyl groups. There is one isolated ethylenic linkage. The environment of the hydroxylic functions and one carboxyl group has been shown t o be as in (XI).Of the known triterpenoids of undetermined constitution remaining, senegenin has a claim to outstanding interest. Investigations directed to a study of the saponin of Polygala senega have spread over many years, but, as mentioned by Simonsen and Ross (I), such "investigations. . . have given rise to very divergent results". I t is this confusion, and its present clarification, which exculpates us from a charge of literary proiiferation in the presentation of incomplete work.Although senega extract has been used medicinally for some time, chiefly as a n expectorant (however, see ref.2 ) , the first results of chemical importance were obtained by Wedekind and Krecke (3). They isolated, by acid hydrolysis of the saponin, a product to which they assigned the formula C26H4406. I t contained two hydroxyl groups, as indicated by the formation of a diacetate, and gave a dimethyl ester.A more extensive study was later reported by Jacobs and Isler (4), who observed the presence of two crystalline sapogenins. T h a t of bwer solubility appeared to be senegenin, although the constants differed somewhat from those of Wedekind and Krecke: the diacetate, in particular, melted a t a much higher temperature. The empirical formula C30H4608 or C30H4408 was proposed, and evidence for an isolated ethylenic linkage found in a weak tetranitromethane test. Titration with alkali indicated the presence of two carboxyl groups (again confirmed by the preparation of a non-crystalline dimethyl ester) and the presence of a lactone was inferred by the consumption of a third equivalent of alkali on heating. Senegenin could not be recovered from the acidified hydrolysis mixture.The second sapogenin isolated from senega root by Jacobs and Isler was an acid, m.p. 257", which appeared to have the empirical formula C31H.5006 or C31H4806. This substance also gave a positive reaction with tetranitromethane, and was shown to give a diacetate. Hydrolysis revealed it to be the monoethyl ester of a dibasic acid. Both the sapogenins gave, on selenium dehydrogenation, the same substituted picene obtained previously from such triterpenoids as oleanolic acid, and shown to be ( 5 ) 1,8-dimethylpicene: results which strongly supported the supposition of Jacobs and Isler that they were dealing with a triterpenoid.