Synthetic Communications

doi: 10.1080/00397917308065909pmid: N/A

Abstract This is a scanned image of the original Editorial Board page(s) for this issue.

Brattesani, Donald N.; Heathcock, Clayton H.

doi: 10.1080/00397917308065910pmid: N/A

Abstract Internal acetylenes are traditionally prepared by the alkylation of terminal acetylenes in liquid ammonia using sodium amide as the base.1 Although the yields of internal acetylenes prepared in this manner are sometimes good, they are usually in the range of 30–60%. Normant has previously pointed out the efficacy of hexamethylphosphoramide (HMPA) as a solvent for alkylations of sodium acetylide.2 In connection with other synthetic work, we have worked out a facile procedure which allows the synthesis of certain internal acetylenes in high yield. A typical experimental procedure follows

Sasaki, Tadashi; Kanematsu, Ken; Yukimoto, Yusuke; Kato, Eiji

doi: 10.1080/00397917308065911pmid: N/A

Abstract Combination of the diazadiene system with three carbon dienophile in the Diels-Alder reaction would provide a synthesis of seven-membered diazaheterocycles. The reaction of 3,6-disubstituted-1,2,4,5-tetrazines with cyclopropene provides a useful route to 2,5-disubstituted-3,4-diazanorcaradienes and 5H-1, 2-diazepines.2 However, in the extensive literature on the Diels-Alder reaction, there are only a few examples of cycloadditions with the azadienes as the 4e components.3 We have examined the reaction of isopyrazole with diphenylcyclo-propenone in the hope of obtaining a convenient synthetic route to the medium-size unsaturated heterocycles. Recently, the reactions of the 4,4-disubstituted isopyrazoles have been indicated to react only with cyclobutadiene4 and 4-phenyl-1,2,4-triazoline-3,5-dione as one of the most potent dienophiles.5

Wenkert, Ernest; McPherson, C. Allen; Sanchez, E. L.; Webb, R. L.

doi: 10.1080/00397917308065912pmid: N/A

Abstract It has been shown recently that β-oxycyclopropanecarboxylic esters, prepared by the cyclopropanation of enol ethers with diazoacetic esters, are cleaved easily on acid hydrolysis.3,4 The following discussion illustrates further examples of this two-step procedure of γ-ketoacid synthesis and related reactions.

Wenkert, Ernest; Buckwalter, Brian L.; Sathe, S. S.

doi: 10.1080/00397917308065913pmid: N/A

Abstract It has been shown recently that β-oxycyclopropyl carbinols are transformed readily into β, γ-unsaturated keto systems on mild acid treatment.1 The following description of the α, α-dialkylation of an aldehyde and of a ring enlargement process illustrates further the great usefulness of the β-oxycyclopropylcarbinyl unit in organochemical synthesis.

Kamata, S.; Uyeo, Shoichiro; Haga, N.; Nagata, W.

doi: 10.1080/00397917308065914pmid: N/A

Abstract An efficient and generally applicable method for stepwise α-alkylatton of esters, nitriles, and ketones via the α-tert-butylthio derivatives is described. The method involves reductive-protonation and reductive-alkylation of α-alkylthio α,α-bis-alkylated carbonyl compounds which are prepared by stepwise alkylation of the corresponding simple α-alkylthio carbonyl precursors. The reduction is conveniently performed by use of stoichiometric amounts of a dissolving metal, particularly lithium, affording correspondingly the α-mono-and the α,α-bis-alkylated carbonyl compounds in good yields.

Golborn, P.

doi: 10.1080/00397917308065915pmid: N/A

Abstract Sulphonate esters, which have numerous applications in organic synthesis, have previously been prepared by the procedure of Tipson.1 This method involves reacting a sulphonyl chloride with an alcohol in dry pyridine, but due to easy alkylation of the solvent, pyridine, by the product2 it is unsuitable for the preparation of reactive sulphonate esters. Several investigators3 have modified the Tipson method and recently Crossland and Servis3 synthesised methanesulphonate esters in high yield from methanesulphonylchloride and an alcohol in the presence of triethylamine as base and dichloromethane as solvent.

Manh Duc, Do Khac; Fétizon, Marcel; Wenkert, Ernest

doi: 10.1080/00397917308065916pmid: N/A

Abstract Recently a new method for α-alkylation of carbonyl compounds, by way of cyclopropanation of their enol ethers and acid-catalyzed hydrolysis of the resultant cyclopropyl ethers, was introduced and applied to a stereospecific angular methylation1 and to the general construction of acyl, quaternary carbon sites.2 The following transformation of ketol, a degradation product of manool,3 into δ8(9)-sandaracopimaradiene (4b),4,5 represents another example of the power of the new synthetic method. In view of a former synthesis of manool3 and the recent interconversion of 4b with isopimaradiene (2a) and sandaracopimaradiene (2b)5 the experiments discussed below complete the total synthesis of the two natural, diterpenic hydrocarbons.6

Posner, Gary H.; Ting, Jen-Shan

doi: 10.1080/00397917308065917pmid: N/A

Abstract Organocuprate(I) reagents are now being widely used for highly selective substitution reactions1 with alkyl,2 alkenyl,2 aryl,2 and acyl3 halides and with α,α'-dihaloketones.4 Organocopper interaction with 1,2-dihaloalkanes is of interest because two main reaction pathways may be expected: (a) replacement of both halogens by organic groups and (b) reductive elimination of halogen to form alkenes.5 We report here that various types of 1,2-dibromides react with lithium dialkyl-cuprate(I) reagents under exceedingly mild conditions to give alkenes exclusively (Eq. 1).

Shalon, Yehuda; Elliott, William H.

doi: 10.1080/00397917308065918pmid: N/A

Abstract In relation to our studies on the metabolism of neutral sterols2 we have prepared several substituted 24-norcholanic acids. Ruthenium tetroxide was selected as the oxidizing agent3,4 in the formation of 24-norcholic acid5,6 from the olefin, 3α, 7α, 12α-triacetoxy-24, 24-diphenyl-5β-chol-23-ene (II), (Fig. 1) since CrO3 provided multiple products5.