ISSN:
0947-3440
Keywords:
1,3-Cycloadditions
;
Sulfines (thione S-oxides)
;
1,2,4-Oxadithiolanes
;
Calculation of TS
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Thione S-oxides (sulfines) harbor the allyl anion MO of 1,3-dipoles, but fail to undergo 1,3-cycloadditions to the usual dipolarophiles with a CC multiple bond. Thioketones stand the test as superdipolarophiles. The thione S-oxides 3 and 9 combined with the thioketones 5 and 7 at 80-100°C, furnishing spiro-1,2,4-oxadithiolanes in high yields despite steric hindrance. The structures of the cycloadducts were clarified by their spectra and an X-ray analysis of 11. Becke3LYP/6-31G* calculations of transition structures and products for the cycloadditions of thioformaldehyde S-oxide to thioformaldehyde support the observed regiochemistry. The activation energy amounts to 3.9 kcal mol-1, in contrast to EA = 17.4 kcal mol-1 for the corresponding addition to ethylene. The transition structures are in accordance with concerted cycloadditions.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.199719970126
Permalink