摘要:

AbstractReaction of the phenalenyl anion (1−) with 1,2‐dibromoethane, 1,4‐dibromobutane and 1,5‐dibromopentane results in the formation of (bromoalkyl)phenalene derivatives. These derivatives undergo ring closure when treated with base to spiro[cyclopropane‐1,1′‐[1H]phenalene](2), spiro[cyclopentane‐1,1′‐[1H]phenalene](4) and spiro[cyclohexane‐1,1′‐[1H]phenalene](5). Reaction of 1−with 1,3‐dibromopropane gives a 1:1 mixture of 1,2,3,5‐tetrahydropyrene (3a) and 1,2,3,6‐tetrahydropyrene (3b), both of which can easily be dehydrogenated to pyrene.Photochemical reactions of spiro[cycloalkanephenalenes]2, 4and5are discussed. The introduction and photochemical opening of a spirocyclopropane ring in phenalene results in the formation of 1,2‐dihydro‐4H‐cyclopenta[cd]phenalene (6), a compound with a fused five‐membered ring. The construction of pyrene and cyclopenta[cd]phenalene skeletons starting from phenalene represents a new approach in the synthesis of polycyclic ar

ISSN:0165-0513    

DOI:10.1002/recl.19901090702

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe reaction with diethyl azodicarboxylate (DEAZD) of different cycloimmonium ylides derived from pyridinium, quinolinium, isoquinolinium and 1‐methylbenzimidazolium bromides (3, 4, 5 and 6) yielded 3‐substituted tetraazapentenes (2). In the special case of 1‐methyl‐3‐phenacyl‐benzimidazolium bromide (6a), the ring cleavage compoundN‐[1‐[(ethoxycarbonyl)amino]‐2‐oxo‐2‐phenylethylidene]‐N‐formyl‐N‐methyl‐1,2‐benzenediamine (7a) was obtained. Its structure was e

ISSN:0165-0513    

DOI:10.1002/recl.19901090703

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe morphinan peptidesN‐(4,5α‐epoxy‐3,6‐dihydroxy‐17‐methyl‐6α,14α‐ethenoisomorphinan‐7α‐carbonyl)‐L‐phenylalanine ethyl ester (4),N‐(4,5α‐epoxy‐3,6‐dihydroxy‐17‐methyl‐6α,14α‐ethenoisomorphinan‐7α‐carbonyl)‐D‐phenylalanine ethyl ester (5) andN‐[N‐(4.5α‐epoxy‐3.6‐dihydroxy‐17‐methyl‐6α,14α‐ethenoisomorphinan‐7α‐carbonyl)glycinyl]‐L‐phenylalanine ethyl ester (6) have been prepared from 4,5α‐epoxy‐3,6‐dimethoxy‐17‐methyl‐6α,14α‐ethenoisomorphinan‐7α‐carboxylic acid (7) and the protected amino acids. The morphinan moiety was coupled to the peptide residue via the acid chloride of 7, after which the morphinan peptides wereO‐demethylated with the aid of hydrogen bromide in glacial acetic acid. The dipeptideN‐glycinyl‐L‐phenylalanine ethyl ester was synthesized via the Excess Mixed Anhydride method (EMA). The new morphinan peptides have been characterized by1H and13C NMR spectroscopy. For conformational analysis, the relative stabilities of two p

ISSN:0165-0513    

DOI:10.1002/recl.19901090704

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe mechanism of cross‐linking of cellulose by glyoxal has been investigated using various alcohols as models for cellulose. Competitive hemiacetalizations of glyoxal show that vicinal diols are much more reactive than isolated alcohols. With a catalyst, both kinds of alcohols react with the hemiacetals, but the isolated alcohols are the most reactive. The main products of acetalization are mixed dioxane bisacetals. Methyl 4‐O‐methyl‐α‐glucoside, considered as a monomeric unit of cellulose, reacts in the same way. The cross‐linking of cellulose by glyoxal is thought to proceed according to the same pattern. The pathways of cross‐linking in the presence of ethylene glycol and diethylene glycol, currently used as co‐reactants of glyoxa

ISSN:0165-0513    

DOI:10.1002/recl.19901090705

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractAggregation of crown‐ether‐substituted phthalocyanines with monovalent metal ions (K+, Rb+, and Cs+) results in cofacially ordered phthalocyanine stacks. Aggregation with Ba2+leads to the formation of phthalocyanine netwo

ISSN:0165-0513    

DOI:10.1002/recl.19901090706

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThree novel carbohydrate surfactants were synthesized by lipase‐catalyzed transesterification of octyl 2‐D‐glucopyranoside, obtained from the acid‐catalyzed reaction of glucose and octanol. The 6‐OH was regioselectively acylated with ethyl octanoate, ethyl acetoacetate and diethyl succinate as acyl‐donating agents. Several lipases have been investigated as biocatalysts. For each esterification, various combinations of lipase, ester and cosolvent were studied, from which a preparative‐scale synthesis was developed. The new compounds were tested for physical properties (melting behaviour, surface tension and CMC): it appears that all 6‐acyl derivatives have surfactant characteristics. The 6‐octanoyl derivative was also found to have liquid

ISSN:0165-0513    

DOI:10.1002/recl.19901090707

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe Mg(ClO4)2‐induced reduction of racemic benzoin by the racemic NADH model compound 3‐(dimethylcarbamoyl)‐1,2,4‐trimethyl‐1,4‐dihydropyridine (1), in accordance to Cram's rule, leads exclusively tomeso‐1,2‐diphenyl‐1,2‐ethanediol. However, whileR‐1 equally reduces 5‐benzoin to affordmeso‐1,2‐diphenyl‐1,2‐ethanediol,S‐1 is reluctant to react withS‐benzoin. The intermediacy of a strictly organized transition state, composed of chelated substrate, dihydropyr

ISSN:0165-0513    

DOI:10.1002/recl.19901090708

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe non‐terminal glycosyl donor, ethyl 2,3‐di‐O‐benzoyl‐5‐O‐(chloroacetyl)‐6‐O‐pivaloyl‐1‐thio‐α‐D‐galactofuranoside, could be used, with the promoterN‐iodosuccinimide and catalytic trifluoromethanesulfonic acid, for the preparation of β‐D‐Galf‐(1→5)

ISSN:0165-0513    

DOI:10.1002/recl.19901090709

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractA methoxy group in 1,2, 3‐trimethoxybenzenes can be readily displaced by a butyl group via reaction with butyllithium in hexane. The reaction probably proceeds via an addition‐elimination mechanism. There appears to be a qualitative relation between the coefficient of the LUMO at the central C‐O carbon atom and the rate of the rea

ISSN:0165-0513    

DOI:10.1002/recl.19901090710

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe terdentate aryldiamine ligand in the aryltantalum(V) alkylidene complex [TaCl2{C6H3(CH2NMe2)2‐2,6}(CHBut)] (1) controls alkylidene reactivity in a range of metal‐mediated Wittig reactions. An X‐ray diffraction study of (1) shows that the hexacoordinate tantalum centre has a very irregular ligand array in which the aryldiamine ligand adopts a newfacialN,C,N coordination

ISSN:0165-0513    

DOI:10.1002/recl.19901090711

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY