摘要:

AbstractA novel synthesis of (+)‐pilocarpine (10a) is described. L‐Histidine is converted into methyl (R)‐2‐bromo‐3‐(l‐methyl‐5‐imidazolyl)propionate (5) in which the configuration has been inverted. Alkylation of dibenzyl ethylmalonate with 5 yields the imidazole compound6, again with inversion. Finally,6is converted into a mixture of (+)‐pilocarpine (10a) and (+)‐isopilocarpine (10b), the separation of whic

ISSN:0165-0513    

DOI:10.1002/recl.19811001202

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

Abstract(E)‐ and (Z)‐3‐(2‐butenyl)‐2,4,4‐trimethyl‐2‐cyclohexen‐1‐one1and2have been isolated from an absolue of Osmanthus Fragrance Lour. and a fusel oil concentrate. Structural proof for these compounds has been obtained via their synthesis from β‐ionone. The key step in this synthesis is the regio‐specific oxidation of 1‐(2‐butenyl

ISSN:0165-0513    

DOI:10.1002/recl.19811001203

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractA safe, efficient and selective method has been developed for the isolation and purification of crown ethers to replace the conventional procedure, which involves repeated vacuum distillations and has reportedly led to destructive explosions. The method is based on the formation of an insoluble 1:1 complex upon stirring a solution of a crown ether in an organic solvent with solid metal salts of 1,n‐alkanedisulfonic acids, such as barium and strontium methanedisulfonate and barium 1,2‐ethanedisulfonate. This extraction procedure can be applied to several crown ethers (including 18‐crown‐6) dissolved in a variety of solvents. Almost quantitative recovery of the crown ether is achieved by continuous extraction with nitromethane.The usefulness of the method was illustrated by isolating 18‐crown‐6 from the crude mixture obtained in the course of its preparation. Whereas conventional workup (including two distillation steps) gave a 25% yield of pure 18‐crown‐6, the CH2(SO3)2Ba‐based method ga

ISSN:0165-0513    

DOI:10.1002/recl.19811001204

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractA number of non‐ionic compounds have been found to form solid complexes with 18‐crown‐6. The highest efficiencies of isolation and the highest selectivities were obtained with nitromethane, dimethyl carbonate and dimethyl oxalate. The usefulness of these compounds was demonstrated in the isolation of>98% pure 18‐crown‐6 from crude reaction

ISSN:0165-0513    

DOI:10.1002/recl.19811001205

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

Abstracttert‐Butylsulfinyl chloride (1) reacts smoothly with tert‐butyl hydroperoxide (2) in the presence of pyridine to afford a variety of products including pyridinium tert‐butylsulfonate, tert‐butyl tert‐butylthiolsulfonate, tert‐butanol and tert‐butylsulfonyl chloride. The mechanistic pathway most likely involves homolytic cleavage of the initially formed tert‐butyl tert‐butyl‐peroxysulfinate (5) via a radical cage process.1H CIDNP effects provide strong evidence in support of the radical pair mechanism. The homolytic dissociation of 5 contrasts with the preferred heterolytic cleavage of peroxysulfonates.Under similar reaction conditions,1reacts with tert‐butyl hydrodisulfide (3) to afford tert‐butylsulfinyl tert‐butyldisulfide (13) in a yield of 90%. As compared with5, thermal decomposition of13is much slower, reflecting the higher SOS bond dissociation energy in13, relative to the low OO bond dissociation energy in5. At elevated temperatures, 13 yields tert‐butyl tert‐butylthiolsulfonate and di‐tert‐butyl tetrasulf

ISSN:0165-0513    

DOI:10.1002/recl.19811001206

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractBicyclo[2.2.0]hex‐5‐ene‐2‐endo‐carboxylic acids and their methyl esters give the corresponding γ‐lactones, together with isomerized products, upon treatment with hydrochloric acid in acetic acid. The reaction mechanism

ISSN:0165-0513    

DOI:10.1002/recl.19811001207

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19811001201

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY