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3. Investigations of the asymmetric intramolecular [2+2] photocycloaddition and its application as a simple access to novel C2-symmetric chelating bisphosphanes bearing a cyclobutane backbone

Author

Haag, Dieter and Scharf, Hans-Dieter

Subjects
Ring formation (Chemistry) -- Analysis, Ligands -- Analysis, Cyclic compounds -- Analysis, Biological sciences, Chemistry
Abstract

Asymmetric intramolecular [2+2] photocycloadditon is a crucial step in the asymmetric synthetic route to new C2-symmetrical disphosphanes with substituted cylcobutane backbone. The cyclodimerization of cinnamates and 2-indenoates was performed on a diol with structurally optimized auxiliary. Intramolecular [2+2] cycloaddition was used to detect several factors that affects the selectivity of the C4DIOP-related ligands. The formation of an 1,4-diradical intermediate was detected as a dominant part of asymmetric intramolecular [2+2] photocycloaddition while cyclization and fragmentation have minor importance in the reaction.

Published
1996

22. IMDA/aldol strategy for transforming carbohydrates into functionalized <TOGGLE>trans-</TOGGLE>decalins

Author

Fraser-Reid, Bert, Chen, Xiao-Tao, Haag, Dieter, Henry, Kenneth J., and McPhail, Andrew T.

Abstract

L-Rhamnal is readily converted into an allyl 2,3-unsaturated-C-glycopyranoside. The (S) configuration of the αL-anomer defines the stereochemical outcome of the future IMDA reaction, leading to the absolute stereochemistry for the trans-decalin moiety in naturally occurring terpenoids. Selective cleavage of the terminal double bond of the allyl group provides an aldehydo function which serves for an aldol/Claisen addition with ethyl sorbate. Of the four possible diastereomers, one is obtained in pure form and processed to give the IMDA precursor. Cyclocondensation is achieved by heating in xylene to give a tricyclic trans-decalin whose structure is established by NMR and X-ray analysis. Chirality 12:488–495, 2000. © 2000 Wiley-Liss, Inc.

Published
2000
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23. Bundeswehr prepares for the Information Age: Part Two.

Author

Kleffner, Klaus and Haag, Dieter

Abstract

Part II. Discusses the strategies, tactics and factors to consider in future battles. Guide questions in defining potential problems in battles; Three basic options for acting in the transparent battlespace; Doctrinal aspects of military command and control which need development; Aims of deep or decisive battle operations.

Published
1999

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