摘要:

AbstractThe acid‐catalyzed rearrangement ofN‐(1′,1′‐dimethylprop‐2′‐ynyl)‐,N‐(1′‐methylprop‐2′‐ynyl)‐, andN‐(1′‐arylprop‐2′‐ynyl)‐2,6‐, 2,4,6‐, 2,3,5,6‐, and 2,3,4,5,6‐substituted anilines in mixtures of 1N aqueous H2SO4and ROH such as EtOH, PrOH, BuOH etc., or in CDCl3or CCl4in the presence of 4 to 9 mol‐equiv. trifluoroacetic acid (TFA)has been investigated (cf. Scheme 12‐25andTables 6 and 7). The rearrangement ofN‐(3′‐X‐1′,1′‐dimethyl‐prop‐2′‐ynyl)‐2,6‐ and 2,4,6‐trimethylanilines (X = Cl, Br, I) in CDCl3/TFA occurs already at 20° with τ1/2of ca. 1 to 5 h to yield the corresponding 6‐(1‐X‐3′‐methylbuta‐1,2′‐dienyl)‐2,6‐dimethyl‐ or 2,4,6‐trimethylcyclohexa‐2,4‐dien‐1‐iminium ions (cf. Scheme 13andFootnotes 26and34) When the 4 position is not substituted, a consecutive [3,3]‐sigmatropic rearrangement takes place to yield 2,6‐dimethyl‐4‐(3′‐X‐1′,1′‐dimethylprop‐2′‐ynyl)anilines (cf. Footnotes 26and34). A comparable behavior is exhibited byN‐(3′‐chloro‐1′‐phenylprop‐2′‐ynyl)‐2,6‐dimethylaniline (45.,cf. Table 7). The acid‐catalyzed rearrangement of the anilines with a Cl substituent at C(3′) in 1N aqueous H2SO4/ROH at 85‐95°, in addition, leads to the formation of 7‐chlorotricyclo[3.2.1.02,7]oct‐3‐en‐8‐ones as the result of an intramolecularDiels‐Alderreaction of the primarily formed iminium ions followed by hydrolysis of the iminium function (orvice versa; cf. Schemes 13,23, and25as well asTable 7). When there is no X substituent at C(1′) of the iminium‐ion intermediate, a [1,2]‐sigmatropic shift of the allenyl moiety at C(6) occurs in competition to the [3,3]‐sigmatropic rearrangement to yield the corresponding 3‐allenyl‐substituted anilines (cf. Schemes 12,14–18, and20as well asTables 6and7). The rearrangement of (−)−(S)‐N‐(1′‐phenylprop‐2′‐ynyl)‐2,6‐dimethylaniline ((−)‐38;cf. Table 7) in a mixture of 1N H2SO4/PrOH at 86° leads to the formation of (−)‐(R)‐3‐(3′‐phenylpropa‐1′,2′‐dienyl)‐2,6‐dimethylaniline ((−)‐91), (+)‐(E)‐ and (−)‐(Z)‐6‐benzylidene‐1,5‐dimethyltricyclo[3.2.1.02′7]oct‐3‐en‐8‐one ((+)‐(E)‐ and (−)‐(Z)‐92, respectively), and (−)‐(S)‐2,6‐dimethyl‐4‐( 1′‐phenylprop‐2′‐ynyl)aniline((−)‐93). Recovered starting material (10%) showed a loss of 18% of its original optical purity. On the other hand, (+)‐(E)‐ and (−)‐(Z)‐92showed the same optical purity as (minus;)‐38, as expected for intramolecular concerted processes. The CD of (+)‐(E)‐ and (−)‐(Z)‐92clearly showed that their tricyclic skeletons possess enantiomorphic structures (cf. Fig. 1). Similar results were obtained from the acid‐catalyzed rearrangement of (−)‐(S)‐N‐(3′‐chloro‐1′phenylprop‐2′‐ynyl)‐2,6‐dimethylaniline ((−)‐45;cf. Table 7). The recovered starting material exhibited in this case a loss of 48% of its original optical purity, showing that the Cl substituent favors the heterolytic cleavage of the N–C(1′) bond in (−)‐45.A still higher degree (78%) of loss of optical activity of the starting aniline was observed in the acid‐catalyzed rearrangement of (−)‐(S)‐2,6‐dimethyl‐N‐[1′‐(p‐tolyl)prop‐2′‐ynyl]aniline ((−)‐42;cf. Scheme 25).N‐[1′‐(p‐anisyl)prop‐2‐ynyl]‐2,4,6‐trimethylaniline(43;cf. Scheme 25) underwent no acid‐catalyzed [3,3]‐sigmatropic rearrangement at all. The acid‐catalyzed rearrangement ofN‐(1′,1′‐dimethylprop‐2′‐ynyl)aniline (25;cf. Scheme 10) in 1N H2SO4/BuOH at 100° led to no product formation due to the sensitivity of the expected product53against the reaction conditions. On the other hand, the acid‐catalyzed rearrangement of the corresponding 3′

ISSN:0018-019X    

DOI:10.1002/hlca.19900730602

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe molecular structure of [1.1.1]propellane has been determined from single‐crystal X‐ray diffraction measurements at 138 K. The crystals of this reactive compound were grown from the melt atca.263 K. The space group isC2, and the asymmetric unit contains four molecules. All have large thermal motion and two show orientational disorder as well. Because of these problems, the atomic positions cannot be determined with high accuracy. Within the experimental limits, the two ordered molecules haveD3hsymmetry, with corrected lengths of central and side bonds ofca.1.60 Å and 1.53 Å, respectively. At lower temperature, the crystals undergo a phase transition. The transition temperature, in the range of 100 to 132 K, varied from one crystal sample to another. All crystals obtained of the low‐temperature phase were twinned, and its space group could not be esta

ISSN:0018-019X    

DOI:10.1002/hlca.19900730603

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractESR, ENDOR, and TRIPLE‐resonance studies are reported on the radical anions of7(1,0),7(2,0), and7(1,1) in which a completely rigid spacer separates two naphthalene π‐moieties by 2, 4, and 6 CC single bonds, respectively. Whereas7(1,0)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}has to be considered as a ‘truly’ charge‐ and spin‐delocalized radical anion of a homobinaphthylene‐like system, the frequency of intramolecular electron transfer in7(2,0)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}and7(1,1)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}is governed by the migration rate of the counterfort (K+) between two equivalent sites at the π‐moieties. Under conditions of tight ion pairing (solvent 2‐methyltetrahydrofuran), the unpaired electron in7(2,0)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}and7(1,1)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}is localized on one π‐moiety and the pertinent spectra resemble that of the radical anion produced from an analogous mononaphthalene derivative8.On the other hand, with solvents of higher cation‐solvating power (1,2‐dimethoxyethane or its mixtures with N,N,N′,N′,N″,N′‐hexamethylphosphoric triamide), delocalization of the electron spin over both π‐moieties becomes evident, thus indicating that the electron‐transfer rate exceeds the hyperfine time‐scale (ca.107s−1). Simultaneous occurrence of ‘localized’ and ‘delocalized’ radical anions is also observed, in particular for7(1,1)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}. Previous findings for the radical anion of6(1) which, like7(1,1)\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}, contains two naphthalene π‐moieties separated by 6 CC single bonds are reinterpreted in the light of the results obtained in the present work. Exhaustive reduction of7(2,0) and7(1,1) leads to the formation oftripletdianions in w

ISSN:0018-019X    

DOI:10.1002/hlca.19900730604

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe convergent syntheses of 3‐deazapurine 2′‐deoxy‐β‐D‐ribonucleosides and 2′,3′‐dideoxy‐D‐ribonucleosides, including 3‐deaza‐2′‐deoxyadenosine (1a) and 3‐deaza‐2′,3′‐dideoxyadenosine (1b) is described. The 4‐chloro‐lH‐imidazo[4,5‐c]pyridinyl anion derived from5was reacted with either 2′‐deoxyhalogenose6or 2′,3′‐dideoxyhalogenose10yielding two regioisomeric (N1and N3) glycosylation products. They were deprotected and converted into 4‐substituted imidazo[4,5‐c]pyridine 2′‐deoxy‐β‐D‐ribonucleosides and 2′,3′‐dideoxy‐D‐ribonucleosides. Compounds1aand1bproved to be more stable against proton‐catalyzedN‐glycosylic bond hydro

ISSN:0018-019X    

DOI:10.1002/hlca.19900730605

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe marine spongeSpongia zimoccaSCHMIDT, 1862, collected in front of the torrent II Rogiolo, south of Livorno, contains the sesquiterpene rogiolol acetate (= (+)‐(2R,3S,6R,8R,9R)‐2,8‐dibromo‐9‐chloro‐1,1,9‐trimethyl‐5‐methylidenespiro[5.5]undec‐3‐ylacetate; (+)‐3a), which represents the first chamigrane isolated from a sponge. Although compounds of this class are common in red seaweeds of the genusLaurencia, and our sponge actually contains 9‐bromochamigrene and a variety of other metabolites of nearby growingLaurenciasp., (+)

ISSN:0018-019X    

DOI:10.1002/hlca.19900730606

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe stereochemical outcome of the base‐catalyzed cyclization of diketones5–8has been investigated under protic conditions (Scheme 3). The more stabletrans‐fused ketols are preferentially formed in kinetically controlled aldol reactions, when the incipient angular substituentR=H(6 →10a) or CN (7→11a,8a→12a). For R = Me (as in5), axial attack of the side‐chain enolate double bond on the ring CO group results in the rather selective formation ofcis‐9b.It is assumed that these cyclizations are controlled by relative product stabilities (product‐like transition state) and steric effects. The competition between fused (e.g.9) and bridged ketol (e.g.13) formation in these cyclizations is discussed. Thecis‐fused (‘steroid’) ketols were readily equilibrated with theirtrans‐counterparts (9b⇄9a,10b⇄10a,11b⇄11a) under aprotic conditions (5 mol‐% of LDA, THF, 0°), thus, allowing

ISSN:0018-019X    

DOI:10.1002/hlca.19900730607

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

Neoflor and 6‐Epineoflor from Flowers ofTrollius europaeus; Highfield1H‐NMR Spectra of (all‐E)‐Neoxanthin and (9′Z)‐NeoxanthinRe‐isolation of the very polar carotenoids from flowers of the title plant furnished two epimeric pentahydroxy compounds. Based on spectroscopical and chiroptical arguments and by chemical correlation with neoxanthin, their structures were established as11(proposed nameneoflor) and12(6‐epineoflor), Decoupling experiments and COSY‐2D‐1H‐NMR spectra allowed a complete assignement of the vinyl protons of the two isomers, and furthermore, for the first time, also of those of (all‐E)‐neoxan

ISSN:0018-019X    

DOI:10.1002/hlca.19900730608

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractFluorescence measurements have been used to follow the build‐up of photoproducts during the direct and benzophenone‐sensitized irradiation of the title compounds 1‐IN, 1‐BrN, and 1‐ClN (HN = naphthalene). Compounds 1‐IN and 1‐BrN react by homolytic dissociation through their lowest triplet and singlet excited states, respectively. Compound 1‐ClN doesnotundergo C–Cl bond fission, except through electron transfer in the presence of an amine A,In the absence of this electron transfer, 1‐ClN reacts only through substitution and

ISSN:0018-019X    

DOI:10.1002/hlca.19900730609

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe photo‐oxygenation of adamantylideneadamantane (1) on siliceous supports using admixed granules of ion‐exchange resin fixed to methylene blue (MB) and rose bengal (RB) gave exclusively the corresponding dioxetane derivative2for the former sensitizer, while the latter gave2and traces of the epoxide3.RB and the charge‐transfer complex produced fromN‐ethylcarbazole and 2,4,5,6‐tetranitrofluoren‐9‐one both reacted with chemically generated singlet oxygen to give superoxide radical anion. Trapping of the latter with 5,5‐dimethyl‐1‐pyrroline 1‐oxide gave an adduct exhibiting a characteristic ESR spectrum. The treatment of1in MeOH with 30% aqueous H2O2for 22 h at 60° gave3in 100% yield. Repetition of this experiment in the presence of 2,6‐di(tert‐butyl)‐p‐cresol caused no significant change. These results indicate that singlet oxygen reacts with1, in the presence of RB, by two different processes. The first leads to dioxetane formation. The second process involves conversion of singlet oxygen by RB to superoxide radical anion which subsequently gives

ISSN:0018-019X    

DOI:10.1002/hlca.19900730610

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

Reductive Co Alkylation of Heptamethyl Cobyrinate with the Methylthiomalonate (S)‐Methyl 3‐Bromo‐2‐[(ethylthio)carbonyl]‐2‐methylpropanoateThe methylthiomalonate(−)‐(S)‐Methyl 3‐bromo‐2‐[(ethylthio)carbonyl]‐2‐methylpropanoate(5a)was prepared from dimethyl methylmalonate in five stepsviathe stereospecific cleavage of the (pro‐S)‐ester group of 1 with pig‐liver esterase in an overall yield of 26.5% (Scheme 4a). Reductive Co alkylation of heptamethylCoβ‐perchlorato cob (II)yrinate (8) with5aby electrosynthesis lead to the alkylcobalt complex9ain 40% yield (Scheme 4b).The O2‐dependent reactions of the methyhnalonyl fragment produced by photolysis of9aand its deuterat

ISSN:0018-019X    

DOI:10.1002/hlca.19900730611

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY