摘要:

AbstractAza Wittig‐type reaction either of iminophosphoranes derived from N‐aminoheterocycles or bis(iminophosphoranes) has been found to be an useful method for the synthesis of the four‐membered ring 1,3‐diazetidine. This account deals with the following cyclization reaction, reactivity and synthetic utility of this ring system and related co

ISSN:0941-1216    

DOI:10.1002/prac.19933350402

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Syntheses and Characterisation of Bisphenyl‐ and Biscyclohexyl‐4,4′‐bibenzyldicarboxylatesA one pot syntheses gives bisphenyl‐4,4′‐bibenzyldicarboxylates (2) or biscyclohexyl‐4,4′‐bibenzyldicarboxylates (3) from bibenzyl (4) and phenols (5) or cyclohexanols (6). 20 compounds2and3with substituents in the p‐position of the peripheric rings have been synthesized; liquid cryst

ISSN:0941-1216    

DOI:10.1002/prac.19933350403

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Protease Catalyzed and Chemical Peptide Bond Formation with α‐Trifluoromethyl Substituted α‐Amino AcidsSubtilisin, α‐chymotrypsin and papain catalyzed hydrolyses of α‐trifluoromethyl substituted N‐benzyloxycarbonyl amino acid methylesters (Z‐TFM‐Xaa‐OMe)1can be achieved only in the case of 3,3,3‐trifluoroalanine. Enzymatic incorporation of Z‐TFM amino acids2into N‐terminal position of dipeptides also fails. In contrary, dipeptides with a TFM amino acid moiety in N‐terminal position, e.g. TFM‐Phg‐L‐Phe‐OMe5, react with H‐Leu‐NH2to give the corresponding tripeptides6in high yield. Z protected dipeptide derivatives8with N‐terminal TFM amino acids can be obtained

ISSN:0941-1216    

DOI:10.1002/prac.19933350404

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Chemoenzymatic Synthesis of13C‐Labeled S‐(‐)‐Malic AcidThe first regio‐ and stereospecific synthesis of S‐(‐)‐13C‐malic acid5with a high incorporation of13C and excellent enantiomeric excess is described. S‐(‐)‐13C‐malic acid5was synthesized in a three‐step reaction starting with ethyl acetate2and diethyl oxalate1. The produced sodium diethyl oxaloacetate3was then enantioselectively reduced with bakers' yeast to S‐(‐)‐13C‐malic acid diethylester4which was

ISSN:0941-1216    

DOI:10.1002/prac.19933350405

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Metal Complex Catalysts with Phosphonic Ester Phosphine Ligands. I. Carbonylation of Methanol by Phosphonic Ester Phosphine Rhodium ComplexesThe treatment of technically available 2‐(chloroethyl)phosphonic acid dimethylester (1) with diphenylphosphine and potassium‐tert.‐butylate affords 2‐(diphenylphosphino)ethylphosphonic acid dimethylester (2a) in a simple way.2acan be used as a hemilabil complex ligand (by phosphine and phosphoryl group.) Rhodium complexes of the type (MeO)2P(O)CH2CH2P(Ph)2RhL3(3) were obtained from2aand exhibit excellent catalytic properties in the liquid‐phase carbonylation of methanol to acetic acid. Studies on other chelat‐ligands did not confirm the exceptional increase of the activity by bisphosphinemonoxyd‐ligands and the inhibition of the title reaction by bisphosphine‐ligands al

ISSN:0941-1216    

DOI:10.1002/prac.19933350406

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Addition of α‐Ketoenamines to 2‐Acetyl‐p‐benzoquinoneAddition of 2‐morpholino‐2‐cyclohex‐1‐en‐one2to 2‐acetyl‐quinone1yields benzo[c][4 H]chromen‐4,7,10‐trion4which is unstable and rearranges to5. 4is converted to 3‐(2,5‐dihydroxy‐phenyl)‐2‐morpholino‐2‐cyclohex‐1‐en‐on3thermically and to dibenzo[b,d]furan‐4‐on7acid catalyzed. The structure of7is secured by independent synthesis. Dibenzo[b,d]furan‐4‐on14is the product of reaction from 2‐(p‐toluidino)‐2‐cyclohex‐1‐en‐on9and1with benzo[c][4 H]chromen‐4,7,10‐trion10as intermediate. By proton catalysis 5‐acetyl‐6‐hydroxy‐carbazol‐1‐on13and 4‐oxo‐cyclohexa[c]isochinolinium hydrochlorid15is obtained from10. 1 H‐cyclopenta[d]furan‐3‐on17is formed by addition of 2‐(p‐toluidino)‐2‐cyclopent‐1‐en‐on16to1. It is rearranged by proton catalysis to 3‐oxo‐1 H‐cyclopenta[c]isochinolinium salt18. Reaction of cyclopentan‐1,2‐dione and1yields 3 aH‐cyclopenta[c]isochromen‐3,6,9‐trion20, rearranging to 1 H‐cyclopenta[b]benzo[d]furan‐3‐on21. The stereochemistry of adducts is discussed in connec

ISSN:0941-1216    

DOI:10.1002/prac.19933350407

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Ring Transformations of Heterocyclic Compounds. I. 2‐Amino‐benzophenones and 7‐Oxo‐hepta‐2,4‐dienenitriles by Reaction of 2,4,6‐Triarylpyrylium Salts with 4‐Nitrobenzyl Cyanide2,4,6‐Triarylpyrylium salts1react with 4‐nitrobenzyl cyanide in the presence of sodium acetate, triethylamine or triethylamine/acetic acid to give 7‐oxo‐hepta‐2,4‐dienenitriles2. With stronger bases such as sodium methanolate or ethanolate a ring transformation of the salts1occurs giving rise to 2‐amino‐benzophenones3which can also be obtained by cyclization of the nitriles2. Under the same conditions the 3‐methyl‐2,4,6‐triphenylpyrylium salt4forms the 4‐methyl‐7‐oxo‐hepta‐2,4‐dienenitrile5by regioselective addition of the 4‐nitrobenzyl cyanide at C‐2 or it is converted to the 2‐amino‐5‐methyl‐benzophenone6. The ring transformation of the pyrylium salts1/4by 4‐nitrobenzyl cyanide represents a new and simple method for the preparation of 2‐amino‐benzophenones. – Spectroscopic data of the novel compounds are discuss

ISSN:0941-1216    

DOI:10.1002/prac.19933350408

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractEthyl 2‐nitrophenyl oxalate (1 a) and its 5‐methoxy derivative (1b) were subjected to catalytic hydrogenations over 3% Pt (S) on carbon in different solvents. Thus, hydrogenation in acetic acid yielded 4‐hydroxy‐2,3‐dioxo‐1,4‐benzoxazine (2a) and its 7‐methoxy derivative (2b) by reductive cyclization, the dehydro forms of the naturally occurring cyclic hydroxamic acids DIBOA and DIMBOA from Gramineae. In contrast, hydrogenation of esters1in methanol results in the formation of amides3by acyl group migration. On heating, amides3undergo lactonization to form lactone‐lactames4, which in turn undergo ring opening to give amides3when re

ISSN:0941-1216    

DOI:10.1002/prac.19933350409

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Synthesis, Structure and Reactions of Epoxyfencholene AldehydeFencholene aldehyde (2), a by‐product of the synthesis of α‐campholene aldehyde (1), can be obtained as main product by fenchane rearrangement of pinocarveol. Epoxidation of the protected fencholene aldehyde (3) gives the trans‐epoxy‐aldehyde (4) which rearranges with Lewis acids to ketone (5) and allylic alc

ISSN:0941-1216    

DOI:10.1002/prac.19933350410

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

α‐Arylamino‐cyanomethylene‐pyrazolinones from Azomethine Dyes and MalonodinitrileThe reaction of azomethine dyes (1a–g) with malonodinitrile (2) gives dicyanomethylene‐pyrazolin‐5‐one (4) which immediately reacts with the eliminated anilines by HCN‐amine exchange giving the deeply coloured arylamino‐cyanomethylene‐pyrazolinones (5a–g). Structural investigations and a study of the absorption charac

ISSN:0941-1216    

DOI:10.1002/prac.19933350411

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY