ISSN:0018-019X    

DOI:10.1002/hlca.19920750102

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

ISSN:0018-019X    

DOI:10.1002/hlca.19920750103

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

Synthesis of Macrocyles by Ring Enlargement of 14‐Membered Cyclic ImidesIn the presence of a base, cyclododecanone derivative2, activated in α‐position by an allyloxycarbonyl group, underwent ring enlargement with isocyanates to give 14‐membered imides (Schemes 1–3). Cleavage of the activating group gave new 14‐membered imides which could be transformed by further ring‐enlargement reactions into new macrocycl

ISSN:0018-019X    

DOI:10.1002/hlca.19920750104

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe photolyses and thermolyses of the α,β‐epoxy silyl ketones5and6are described. On n,π*‐excitation, the silyl ketones5and6were transformed to the ketone7and the ketene8in quantitative yield. The formation of8may be explained by initial cleavage of the C(α)O bond and subsequent C(1)→C(2) migration of the (t‐Bu)Me2Si group. In contrast to the acylsilanes5and6, the photolyses of the analogous methyl ketones11and12gave a very complex mixture of products. On thermolysis,5and6yielded the ketone7and the acetylenic compound9, which were probably formedviaa siloxycarbene intermediate. In addition, the 1,3‐dioxle10was formedviaan initial C(α)C(β) bond cleavage leading to the ylidegand subsequent intramolecular addition of the carbonyl group. The analogous 1,3‐dioxole13was obtained on pyrolysis of the

ISSN:0018-019X    

DOI:10.1002/hlca.19920750105

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractResults are reported for high‐energy beam experiments which establish the formation of endohedral carbon cluster‐noble gas compounds by bimolecular reactions of C xn+(x = 60, 70;n= 1, 2, 3) with He and C 60+·with Ne. The ions were accelerated up to 8 ke V in a four‐sector mass spectrometer and allowed to collide with the noble gas in a collision chamber at room temperatur. Product ions were monitored with a B/E = constant linked scan. Within the sensivity of the experiments, no carbon cluster‐gas compounds were observed in the reactions of C 60+·with H2, D2, O2, Ar, and SF6, or of C 70+·with O2. The observed fall in the cross‐section for carbon cluster‐noble gas compounds with increasing size of the noble gas, the observation of unimolecular loss of C2from mass‐selected CxHe+ions, and the elimination of carbon fragments instead of He observed in the formation of the collision‐induced CxHen+product ions are taken as evidence for endohedral compound formation. Results ofab initiomolecular‐orbital calculations for the perpendicular penetration of the plane of ionized benzene with He, Ne, and Ar indicate that sufficient kinetic energy should be available in the collisions with C 60+·to penetrate the C 60+·cage at the col

ISSN:0018-019X    

DOI:10.1002/hlca.19920750106

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe synthesis and properties of the molecular reduction device7b(CoII–V 5++) consisting of a reduction catalyst (a derivative of vitamin B12, CoII) and a covalently linked 10‐electron reservoir (five viologen units, V++) is described. The five viologen subunits were introduced at C(2) and C(3) of the side chainscand g and b,eandf, respectively, of an appropriate derivative of heptamethyl cob(III)yrinate byN‐alkylation of 1‐methyl‐4,4′‐bipyridinium iodide (seeScheme). The pentaviologen‐linked corrinatocobalt(II) complex7bbehaves as a molecular electron trap with respect to the CoIII/CoIIredox couple. The phenomenon is related to the structural and thermodynamic relation of the corrin and viologen subunits in7b, i.e. the relative redoc energies and the spherical inner‐outer arrangement of the types of redox systems. When completely reduced to CoI–V 50,7bexhibits multiple reductive elimination oftrans‐1,2‐dibromocyclohexane to cyclohexene under concomitant oxidation to CoII–V 5++. Rate measurements indicate that the reduction occursviaCoIwhich is regenerated by intramolecular electron transfer from the periphery of

ISSN:0018-019X    

DOI:10.1002/hlca.19920750107

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractChiral acylnitroso dienophiles14, which were obtained fromL‐proline and fromD‐mandelic acid, reacted with cyclohexa‐1,3‐diene to give the expected diastereoisomers15and16(Scheme 2andTable 1). Thed.e.values for theseDiels‐Alderreactions were moderate; they are related to the molecular stiffness of the dienophiles. The absolute configuration of the major cycloadducts was interpreted in terms of HOMO/LUMO interactions, the approach being ‘endo’ and the acylintroso dienophiles reacting from their s‐c

ISSN:0018-019X    

DOI:10.1002/hlca.19920750108

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

[(1,3‐Dioxolan‐2‐ylidene)methyl]phosphonates and ‐phosphinates as [simple] Synthons in Heterocyclic SynthesisThe readily available [(1,3‐dioxolane‐2‐ylidene)methyl]phosphonates and ‐phosphinates2a–f(Scheme 1) can be transformed with amines to aliphatic ketene N,O‐and N,N‐acetales (seeScheme 2,2a→3–7). Alkanediamines yield with2a–fthe imidazolidines8a–fand the hexahydropyrimidines9a–d(Scheme 3). the oxazolidine derivatives10a–eand the thiazolidine11are accessible under special reaction conditions starting from2a, b(Scheme 4). Hydrazines react with the CN‐group‐containing ketene O,O‐acetals2a–cto the pyrazoles12a–g, whereof12a, d, ecan be cyclized to pyrazolo[1,5‐a]pyrimidines13a–d(Scheme 5). Amidines as starting materials transform2a–cin an analogous

ISSN:0018-019X    

DOI:10.1002/hlca.19920750109

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractA stereodivergent synthesis of enantiomerically pure E‐nor‐15‐azayohimbinesviacondensation of tryptamine with derivatives of pyroglutamate4is reported. When thePictet‐Spenglerreaction was induced in refluxing aqueous AcOH a nearly equimolar ratio of lactams7and8was obtained, whereas under kinetic control (TFA, room temperature) thetrans‐derivative8was the major product. In contrast, cyclization of amido acetal12with TsOH gave thecis‐derivative7as preponderan

ISSN:0018-019X    

DOI:10.1002/hlca.19920750110

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe template reaction of {bis[(S)‐2‐(aminomethyl)pyrrolidine]}copper(II) with formaldehyde, nitroethane, and base in MeOH yields optically pure {1,7‐bis[(S)‐pyrrolidin‐2‐yl]‐4‐methyl‐4‐nitro‐2,6‐diazaheptane}‐ copper(II) ([Cu((S,S)‐mnppm)]2+) in high yield. The same reaction withrac‐2‐(aminomethyl)pyrrolidine is also described. Preparative details and spectroscopic and electrochemical properties of the CuIIcomplexes and of the free ligands are reported and compared with structural, spectroscopic and electrochemical data of the CuIIcomplex of the unsubstituted parent ligand 1,7‐bis[(S)‐pyrrolidin‐2‐yl]‐2,6‐diazaheptane (ppm). The crystal structure of [Cu(ppm)]Cl ClO4has b

ISSN:0018-019X    

DOI:10.1002/hlca.19920750111

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY