摘要:

AbstractAcyclic acceptor‐substituted conjugated enynes bearing sulfonyl sulfinyl, sulfonate, nitro, amide, cyano, and oxazolidino groups at the double bond were synthesized and the regioselectivity of their reaction with organocuprates was examined. All Michael acceptors except enynes with nitro and amide functions underwent 1,6‐additions, and the allenyl enolates thus formed were trapped with electrophiles in order to obtain the corresponding allenes. A qualitative reactivity scale for these reactions was established. The dependence of the regioselectivity of both the cuprate addition and the subsequent electrophilic capture on the acceptor group and the substitution pattern of the allenyl enolate were studied. Cyclic 2‐en‐4‐ynoates with endocyclic double bonds were synthesized and treated with organocuprates to afford an exocyclic allene in

ISSN:0009-2940    

DOI:10.1002/cber.19951280902

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe rate of enantiomerization of the racemic α‐phenylselenoalkyllithium compound6has been determined by dynamic NMR spectroscopy in [D8]THF. The enantiomerization rate was found to be first order with respect to monomeric6and to show no conspicuous solvent dependence (diethyl ether; toluene + 1 eq. of THF) or change upon addition of LiClO4. The marked steric effects on the enantiomerization rate found with the α‐duryl‐ and α‐mesityl‐selenoalkyllithium compounds7cand7dsuggest that rotation about the carbanion‐selenium bond may be the rate‐determining step in those sterically hindered systems. Similar steric effects were detected for the enantiomerization of the corresponding α‐arylthio‐ and α‐aryltelluroalkyllithium compounds7jand7f, but are absent with the α‐arylsilyl‐substituted alkyllithium compound7o. This finding, along with the fact that the phenyltelluro‐ (7e), phenylseleno‐ (6), and phenylthio‐alkyllithium compounds (7g) have essentially the same enantiomerization barrier, lead us to propose that in these cases a reorganization within the contact ion pair is the rate limi

ISSN:0009-2940    

DOI:10.1002/cber.19951280903

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA variety of monosubstituted γ‐lactols4–6were prepared in good yields by DIBAL reduction of the corresponding γ‐lactones1–3. The monophenyl‐substituted lactols4b–6bwere transformed into disubstituted tetrahydrofuran derivatives by replacement of the hydroxyl group by the alkyl residue of organometallic compounds used as nucleophiles. The diastereoselectivity of the substitution was found to depend strongly on the substitution pattern of the γ‐lactols. For the reaction of the 3‐ and 4‐substituted derivatives4band5b, respectively, good to excellenttransselectivity was observed, while the 5‐substituted derivative reacted without any diastereoselectivity. These results were interpreted by means o

ISSN:0009-2940    

DOI:10.1002/cber.19951280904

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe mononuclear rhodium complexes [(C5H5CH2C5H4)‐Rh(CO)2] (1) and [(C5H5CH2C5H4)Rh(PhCCPh)(PiPr3)] (2) readily react withnBuLi or TlOEt to yield the corresponding lithium salts3and4or thallium salts5and6. The reaction of these salts with [(C5H5)Nb(NtBu)Cl2] (7) leads to the formation of the heterodinuclear compounds [{CH2(C5H4)2}‐{Rh(CO)2}{(C5H5)Nb(NtBu)Cl}] (8) and [{CH2(C5H4)2}‐{Rh(PhCCPh)(PiPr3)}{(C5H5)Nb(NtBu)Cl}] (9), respectively. Treatment of3–6with [Mo(NtBu)2Cl2] (10) gives the heterodinuclear Rh/Mo complexes [{CH2(C5H4)2}{Rh(CO)2}‐{Mo(NtBu)2Cl}] (11) and [{CH2(C5H4)2}{Rh(PhCCPh)‐(PiPr3)}{Mo(NtBu)2Cl}] (12). The analogous reaction of [Mo(NMes)2Cl2(DME)] (13) with3–6yields the corresponding complexes [{CH2(C5H4)2}{Rh(CO)2}{Mo(NMes)2Cl}] (14) and [{CH2(C5H4)2}{Rh(PhCCPh)(PiPr3)}{Mo(NMes)2Cl}] (15). From the monometallated ligand [(C5H5CH2C5H4)M] (M = Li:16; M = Tl:17) and the imidometal compounds7, 10and13, the mononuclear complexes [(C5H5CH2C5H4)(C5H5)Nb‐(NtBu)Cl] (18) and [(C5H5CH2C5H4)Mo(NR)2Cl] (R =tBu:19; R = Mes

ISSN:0009-2940    

DOI:10.1002/cber.19951280905

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractPentacarbonyltungsten‐coordinated thiobenzaldehyde, [(CO)5W{S=C(Ph)H}] (1), reacts with 1‐methylthio‐1‐propyne, 1‐ethylseleno‐1‐propyne, and alkoxyethynes by insertion of the CC into the S=C bond to form in a highly regio‐and stereoselective manner the α,β‐unsaturated dithio, selenothiono, and thionocarboxylic ester complexes (E)(CC)‐[(CO)5W{η1‐SC(XR′)C(R)=C(Ph)H}] (3) (R = Me: XR′ = SMe (a), SeEt (b); R = H: XR′ = OEt (c), OtBu (d)). The analogous reaction of1with bis(alkylthio)ethynes affords mixtures of the (E) and (Z)(C=C) isomers of [(CO)5W{η1‐S=C(SR)C(SR)=C(Ph)H}] (6) [R = Me (a),tBu (b)]. TheZisomers are the initially formed products. Formation of (Z)‐6is followed by Z →Eisomerization until an equilibrium [E/Z= 1 (6a), 1.5 (6b)] is obtained. For R =tBu isomerization is significantly faster than for R = Me. The dithio and thiono ester ligands can be cleaved intact from the metal by treatment with [NEt4]Br as shown by the examples of3a, 3c, and6a. Complex3chas been ch

ISSN:0009-2940    

DOI:10.1002/cber.19951280906

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractTwo reaction pathways for the synthesis of 1,3,5‐triaza‐7‐phosphoniaadamantane salts, RP[(CH2)6N3]+X‐(1), were followed. Route 1 starts with commercial tetrakis(hydroxymethyl)phosphonium chloride, which is converted into P(CH2OH)3by treatment with a base. Subsequent quaternization with alkyl halides RX and cyclization with formaldehyde and ammonia afford [R‐TPA]+X‐. This process is only applicable for R = Me (1a) and Et (1b), however. Route 2 is more general and starts with primary phosphanes RPH2, which are converted into organotris(hydroxymethyl)phosphonium salts with formaldehyde and hydrochloric acid followed by ring closure with CH2O/NH3to give compounds1c–1f(R =t‐Bu,c‐Hex, Bz, and Ph, respectively, and X = Cl, I, PF6, or BPh4). Reductive cleavage of compounds1by sodium in liquid ammonia proceeds with either external (P‐R) or internal (P‐CH2) bond rupture. P‐R cleavage affords the 1,3,5–triaza‐7‐phosphaadamantane (TPA), while cage cleavage leads to new bowl‐ or helmet‐shaped ligand systems with peripheral amine and phosphane functions (2). Yields of the cage‐opening reaction are highest for R = Ph (2f), moderate for R = Me and Et (2a, 2b), and poor with the remaining R groups (2c–2e). A radical mechanism is proposed for this reaction, the leaving group properties of R determining the direction of the cleavage. The crystal and molecular structures of compounds2aand2fwere determined by X‐ray diffraction studies.Exopositions were found for the N‐Me and P‐R groups. The isomers with the R group in theendoposition are also present in solution in small amounts, as detected by NMR spectroscopy. Isomer interconversion by P inversion is slow on the NMR time scale. Compounds2a, 2band2fwere oxidized with elemental sulfur and selenium to give the monosulfides and selenides, respectively (2aS, 2aSe, 2bS, 2bSe, 2fS, 2fSe). Oxidation with H2O2led to degradation. Compound2awas quaternized at the P atom by treatment with Mel to give the corresponding phosphonium salt. Treatment with equimolar quantities of (Me2S)AuCl led to the 1:1 complexes2aAucl, 2bAuCland2fAuCl, with the AuCl units solely P‐bonded, as determined by X‐ray diffraction of2aAuCland2fAuCl. Compound2aforms an ionic 2:1 complex with AuCl, composed of the ions [(2a)2Au]+Cl‐(with unidentate ligands), while its reaction with [Me2AuCl]2leads to [Me2Au(2a)]+[Me2AuCl2]‐(with a chelating2aligand), as again confirmed by crystal structure analysis in both cases. Ligands2a, 2band2falso act as chelating ligands in their tetracarbonylmolybdenum com

ISSN:0009-2940    

DOI:10.1002/cber.19951280907

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

Abstract1,4‐Bis(diphenylphosphanylmethyl)benzene (1) was converted into its bis[chlorogold(I)] complex [1 · (AuCl)2] upon treatment with two equivalents of chloro(dimethyl sulfide)‐gold(I). The reaction of1 · (AuCl)2with one equivalent of silver tetrafluoroborate afforded a cyclic di[gold(I)]chloronium tetrafluoroborate [1· Au2Cl+BF‐4]. Substitution of chloride in1 · (AuCl)2by sodium methanethiolate in wet chloroform, gave the bis[methylthiogold(I)] complex1 · (AuSMe)2], while with sodium sulfide a cyclic complex1 · Au2Swas obtained. Reaction of1 · (AuCl)2with two equivalents of AgBF4followed by treatment with diphenyldisulfide or sodium methanethiolate yielded the cyclic methyl/phenylsulfonium tetrafluoroborates1 · Au2SPh+BF‐4and1 · Au2SMe+BF‐4, respectively. All compounds were identified on the basis of their analytical and spectroscopic data. The crystal structures of1 · (AuCl)2,1 · (AuSMe)2, and1 · Au2Shave been determined. The Au2S complex has a cyclic structure with a narrow Au‐S‐Au angle of 86.7(1)° indicating a significant intr

ISSN:0009-2940    

DOI:10.1002/cber.19951280908

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe reaction oftert‐butanethiol with tris[(triphenylphosphane)gold(I)]oxonium tetrafluoroborate in dichloromethane in the presence of sodium tetrafluoroborate gave quantitative yields of a product {Me3CS[Au(PPh3)]2}+BF‐4(1). In the crystal lattice of this salt, the sulfonium cations are associated into dimers through close Au…Au contacts. The centrosym‐metrical tetranuclear unit has Au…Au distances of 3.292(1) and 3.206(1) Å, and the Au‐S‐Au angles are exactly 90.0(1)°. Both data are indicative of significant intra‐ and intercationic Au…Au attractions. The analogous reaction of ethane‐1, 2–dithiol afforded high yields of a product {(CH2S)2[Au(PPh3)]3}+BF‐4(2). The compound is fluxional in CD2Cl2solution and shows only one31P‐NMR signal at ‐60°C. In the crystal, the quasiC2‐symmetrical trinuclear cations feature the sulfur atoms in bridging positions between two gold atoms. The central gold atom is thus three‐coordinate; the peripheral gold atoms are two‐coordinate with Au…Au contacts at 3.284(1) and 3.129(1) Å and Au‐S‐Au angles as small as 86.5(1) and 81.0(1)°. This provi

ISSN:0009-2940    

DOI:10.1002/cber.19951280909

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractDehalogenation of halide precursors [(olefin)RhCl]2[olefin = ethylene, 1,5‐cyclooctadiene (COD], norbornadiene (NBD), 2,3‐dimethylbutadiene (DMB)]in water gave the respectivecis‐diolefin aqua ions, characterized by NMR spectroscopy in solution. Attempted isolation of the tosylate salt [(COD)Rh‐(H2O)2]OTs yielded crystals of (COD)Rh(H2O)(η1‐OTs) characterized by X‐ray structural analysis. [(NBD]Rh(H2O)2]SbF6in the presence of adventitious toluene decomposed into [(NBD])Rh(η6‐toluene)]SbF6and [(NBD]2Rh]SbF6, both complexes were isolated and structurally characterized. Ethylene exchange in [(C2H4)2Rh(H2O)2]+is fast withk2of the order of 104–105s‐1· M‐1. The rate constant for water exchange in [CODRh(H2O)2]+is estimated as 104s‐1(ΔDLG

ISSN:0009-2940    

DOI:10.1002/cber.19951280910

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe aldol reaction in the presence of titanium halides is described. Good yields of aldols10–17were obtained even with only catalytic amounts of titanium tetrafluoride. The reactions were carried out in the absence of a bas

ISSN:0009-2940    

DOI:10.1002/cber.19951280911

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY