ISSN:0165-0513    

DOI:10.1002/recl.19881070902

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractFriedel‐Crafts alkylation of pyrene with 2,5‐dichloro‐2,5‐dimethylhexane and 2,4‐dichloro‐2,4‐dimethylpentane in carbon disulfide yields 7,7,10,10‐tetramethyl‐7,8,9,10‐tetrahydrobenzo[a]pyrene and 7J,9,9‐tetramethyl‐8,9‐dihydro‐7H‐cyclopenta[a]pyrene, respectively, both in 99% yield. Alkylation with 1,4‐dichlorobutane, followed by aromatization, yields benzo[a]pyrene in a facile two‐step synthesis in 8% yield. A mechanism is proposed which rationalizes the fact that only one ring of pyrene undergoes substitution. The1H‐1H NMR coupling constants of t

ISSN:0165-0513    

DOI:10.1002/recl.19881070903

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractCyclometallated platinum complexes of the monoanionic ligand 2‐NMe2C6H4CH(SiR3)−(R = Me, Ph; dmat‐SiR3−) have been synthesized via the reaction of the organolithium reagent with both [PtCl2(Et2S)2] and [PtCl2(Et2COD] (COD = 1,5‐cyclooctadiene). The 1:1 reaction of Li(dmat‐SiR3) with [PtCl2(Et2S)2] affords the mono‐alkylated platinum complexes [PtCl(dmat‐SiR3)Et2S]. The X‐ray crystal structure of one of these (R = Me) was determined. The platinum centre has a square‐planar geometry with atrans‐C‐Pt‐Cl arrangement and the chelate dmat‐SiMe3ring has a conformation that places the bulky SiMe3substituent out of the aryl ring plane. From the 2:1 reaction of Li(dmat‐SiR3) with [PtCl2(Et2S)2] no stable organoplatinum compound could be isolated. However with [PtCl2(Et2S)2COD] this 2:1 reaction affords complexes of [Pt(dmat‐SiR3)2COD] stoichiometry. These latter monomeric complexes contain one cyclometallated dmat‐SiR3ligand and a COD ligand that, after having undergone an addition of the second dmat‐SiR3ligand to one of its double

ISSN:0165-0513    

DOI:10.1002/recl.19881070904

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe homogeneous sulfonations of 1,3‐dihydroxybenzene (1), its monomethyl (2) and dimethyl ether (3) in concentrated aqueous sulfuric acid at 25°C have been studied and isomer distributions and rate coefficients for the sulfonation of1–3and their monosulfonic acids are reported. The initial process, upon dissolution of the reactants, is protonation at C(4) and C(6). The subsequent sulfonation of the symmetrical reactants1and3yields the 4‐sulfonic acids and that of2the 4‐ and 6‐sulfonic acids, the ratio of which is 0.8 + 0.1 at 73.5% H2SO4. The sulfonation of the 4‐sulfonic acid of1(1‐4‐S) yields a mixture of 2,4‐ and 4,6‐disulfonic acids, that of2‐4‐S and3‐4‐S yields the 4,6‐S2and that of2‐6‐Sgives a mixture of 2,6‐ and 4,6‐S2. The disulfonic acids1‐2,4‐S2and2‐2,6‐S2both slowly isomerize to yield the 4,6‐disulfonic acid isomers. At acid concentrations ≥ 82.8% H2SO4, the disulfonic acids of1slowly yield1‐2,4,6‐S3, whereas those of2and3are not further sulfonated. The absence of2‐2,4‐S2from2‐4‐S and of2‐2,4,6‐S3and3‐2,4,6‐S3is discussed in ter

ISSN:0165-0513    

DOI:10.1002/recl.19881070905

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe photochemistry of the α‐phenyl‐β,γ‐enones3–6has been studied under conditions of direct (λ 300 nm) and triplet‐sensitized irradiation.Upon direct irradiation,3exhibits decarbonylation, a 1,3‐acyl shift (1,3‐AS) and an oxa‐di‐π‐methane (ODPM) rearrangement. Under the same conditions,4, on the other hand, affords only the ODPM product whereas5gives the decarbonylation,1,3‐AS and ODPM products. The formation of the ODPM product of5is efficiently quenched by triplet quenchers in contrast to the ODPM products of3and4, the quantum yields of which are not reduced upon the addition of typical triplet quenchers. Triplet‐sensitized irradiation of5leads to the ODPM rearrangement, whereas surprisingly3and4are unreactive. It is suggested that the ODPM rearrangement, upon direct irradiation of3and4, proceeds from theS2(ππ*) state. The ODPM product formed upon direct irradiation of5is thought to be formed from theT1(ππ*) state populated by ISC from theS1(nπ*) state.Upon direct irradiation,6exhibits a reversible 1,3‐AS and in addition ketene formation via an intramolecular 1,5‐H shift. Under conditions of triplet photosensitization, compound6appears to be stable.Given the apparently different photochemical behaviour of these constrained compounds, a general reactivity pattern for the direct and sen

ISSN:0165-0513    

DOI:10.1002/recl.19881070906

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe asymmetric addition of MeLi to di‐p‐tolylsulfine1in the presence of the chiral ligands (2S,2′S)‐2‐(hydroxymethyl)‐1‐[(1‐methylpyrrolidin‐2‐yl)methyl]pyrrolidine2, (2S)‐2‐hydroxymethyl‐1‐methylpyrrolidine4, (2S,2′S)‐2‐(methoxymethyl)‐1‐[(1‐methylpyrrolidin‐2‐yl) methyl]‐pyrrolidine5and (2S,2′S)‐2‐(1‐hydroxy‐1‐propylbutyl)‐1 ‐[(1‐methylpyrrolidin‐2‐yl)methyl]‐pyrrolidine6was investigated. The influence of the molar ratio of substrate, MeLi and ligand, of temperature and of solvents on the enantiomeric excess of the sulfoxide3was studied for ligand2.The optical yield varied from 5‐55%. The highest enantiomeric excess (55%) for the sulfoxide3was obtained using ligand2(ratio sulfine1/MeLi/ligand2= 1.0/6.7/4.0) in tetrahydrofuran at ‐ 78°C. The results are discussed by comparing them with the enantios

ISSN:0165-0513    

DOI:10.1002/recl.19881070907

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractS,S‐diphenyl phosphorodithioates of appropriately protected serine and tyrosine have been prepared. In the case of serine, neighbouring group participation of a free N‐or C‐terminus on the corresponding triester functions leads to the formation of aziridine and phosphoserine derivatives, respect

ISSN:0165-0513    

DOI:10.1002/recl.19881070908

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractBiologically interesting allylic phosphates have been prepared by a novel route starting from silylated alcools.

ISSN:0165-0513    

DOI:10.1002/recl.19881070909

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19881070911

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19881070912

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY