Willy Friedrichsen

Intramolecular cycloadditions with isobenzofurans. I

Etude des cyclisations intramoleculaires des methoxy-5 hexene-5yl-1 benzo [c] furanne et methoxy-6 pentene-4yloxy-3 benzo [c] furannecarboxylate-1 de methyle respectivement en epoxy-4a,9 methoxy-7 octahydro-1,2,3,4,4a,9,10,10a phenanthrene et epoxy-6,10b hexahydro-2,3,4,4a,5,6 methoxy-8 naphto [1,2-b] pyrannecarboxylate-6 de methyle

Intramolecular cycloadditions with isobenzofurans - X. 1 a novel synthesis of annulated hydroquinolines

Abstract The intramolecular Diels-Alder reaction of a l-amino substituted isobenzofuran 3 leads to hydrobenzo/h/ quinolines (5 6).

Nonclassical furoxans — A computational study

Ab initio and density functional theoretical studies on nonclassical furoxans (4a-c; 9, 10; 15, 16; 21a, b; 23, 24) and some of their open-chain o-dinitroso isomers (5a-c; 6a-c; 7a-c; 11–14; 17–20; 22a, b; 25, 26) are presented.

Pyryliumolate 1. - Ein einfacher zugang zu anellierten benzotropolonen

Abstract The synthesis of benzotropolones, 4a,b utilizing an intramolecular 1,3-dipolar cycloaddition reaction with benzopyryliumolates ( 2a,b; generated in situ) is reported.

Synthese eines oxepino[2,3-d]isoxazol-systems

Abstract The reaction of the transient furoisoxazole 4 with dimethyl acetylenedicarboxylate results in the formation of oxepine 9k . The boat-shaped structure of 9k has been confirmed by X-ray crystallography. The experimental findings are in accord with quantum chemical calculations (AM1, PM3).

Intramolecular Cycloadditions with Isobenzofuran -VIII. Synthesis of Precurosors via an Oppé Reaction

Synthese de diazomethyl-2 methoxy-4 benzoates de pentene-4 yles qui, par addition de Diels Alder intramoleculaire, conduisent a des cyclopenta [d] naphto [1,2-b] pyrannes

A density functional theoretical study of nonclassical furoxans

Abstract Calculations on nonclassical furoxans ( 6a–c , 7a–c , 8a–c , 9a–c ) and their anti -1,2-dinitroso isomers ( 10a–c , 11a–c, 12a–c ) using density functional theoretical methods employing Beckes three-parameter exchange with the Lee, Yang and Parr correlation functional (Becke3LYP/6-31G * ) are reported.

Pyryliumolates II—generation of and cycloaddition reactions with isoxazole annulated pyryliumolates

Isoxazole annulated pyryliumolates (formed in situ from diazo compounds 3 and 6) can be trapped with DMAD to form 1:1 adducts (5,8) and in minor amount 2:1 adducts (Schemes 4 and 5). Suitably substituted pyryliumolates (7b,c) undergo an intramolecular cycloaddition giving 9 and 10. Compound 10 can be transformed easily to an annulated tropolone (11). Computational studies on 2:1 adducts and on 11 are reported.

Intramolecular cycloadditions with isobenzofurans .12. Synthesis and reactions of furo[3,4-d]isoxazoles

The synthesis of furo[3,4-d]isoxazoles (3) and inter- and intramolecular cycloaddition reactions (to 4, 5a,b) are reported. The structures of 3k, 5b and 6 have been clarified by X-ray crystallography. Quantum chemical calculations (AM1, PM3, ab initio, density functional methods) concerning the geometry and the different reactivity of benzo[c]furans and furo[3,4-d]isoxazoles were performed.

Reaktionen mesoionischer Fünfringheterocyclen mit o-chinoiden Verbindungen, VII [1]. Thermische [π4+π4]-Cycloadditionen eines bicyclischen Imidazolo[1,2-c]thiazolsystems / Reactions of Mesoionic Five-Membered Heterocycles with o-Quinoid Compounds, VII [1]. Thermal [π4+π4]Cycloadditions of a Bicyclic Imidazolo[1,2-c]thiazole System

5-(4-Methylphenyl)-2,7-diphenyl-4-phenylcarbamoylimidazolo[1,2-c]thiazol (9) reacts with tetrachloro-o-benzoquinone to give a [π4+π4]cycloadduct (17); in an obviously analogous manner 5-(4-methylphenyl)-2.7-diphenylimidazolo[1,2-c]thiazol (8) with N, N′-benzenesulfonyl-obenzoquinonediimine (14) yields compound 16 and benzenesulfinic acid. The [π4+π4]adduct 17 solvolyzes with alcohols in a stereoselective SN2″ reaction giving 24a, b. The stereochemical outcome of this reaction has been determined by an X-ray analysis of 24a.