Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The enthalpies of formation ΔHf and the ring strain energies Eg were calculated for the nine isomeric dithiacyclooctynes 1--9 by applying the MNDO method. Reaction Scheme 2 shows the synthesis of 1,4-dithia-2-cyclooctyne (1), which was the highest Eg value in this series. It dimerizes to 13 in the absence of reaction partners. Scheme 4 summarizes the preparation of 1,5-dithia-2-cyclooctyne (2) and its homologue 1,5-dithia-2-cyclononyne (23) and Scheme 6 the preparation of 1,4-dithia-6-cyclooctyne (6) and its homologue 1,5-dithia-7-cyclononyne (29). Depending on the position of the sulfur atoms, all three reaction sequences contain different steps for the introduction of the triple bonds.
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