Intramolecular 1,4-Dipolar Cycloadditions of Cross-Conjugated Heteroaromatic Betaines. Synthesis of Hexahydrojulolidines and Related Peri- and Ortho-Fused Ring Systems
Φόρτωση...
Ημερομηνία
Συγγραφείς
Potts, K.T.;
Rochanapruk, T.;
Padwa, A.;
Coats, S.J.;
Hadjiarapoglou, L.
Τίτλος Εφημερίδας
Περιοδικό ISSN
Τίτλος τόμου
Εκδότης
American Chemical Society
Περίληψη
Τύπος
Είδος δημοσίευσης σε συνέδριο
Είδος περιοδικού
peer reviewed
Είδος εκπαιδευτικού υλικού
Όνομα συνεδρίου
Όνομα περιοδικού
J. Org. Chem.
Όνομα βιβλίου
Σειρά βιβλίου
Έκδοση βιβλίου
Συμπληρωματικός/δευτερεύων τίτλος
Περιγραφή
3-Alkenyl2-lactams react with (chlorocarbony1)phenylketene to give nonisolable anhydro-4-hydroxy-2-oxo-1,3-oxazinium hydroxides which undergo regio- and stereospecific 1,4-dipolar cycloaddition in moderate yields to produce cycloadducts containing a carbon dioxide bridge. Thermolysis of the cycloadduct led to extrusion of carbon dioxide via a nonconcerted 1,5-hydrogen shift to give julolidinetype derivatives. Two of the cycloadducts were characterized by single-crystal X-ray determinations. A significant enhancement in the overall yield of the cycloaddition occurred in related reactions using anhydro-4-hydroxy-2-oxo-1,3-thiazinihuym droxides obtained from 3-alkenyl-3-ethyl(or methyl) 2-thiolactams and a variety of 1,3-bielectrophiles such as (chlorocarbonyllphenylketene, carbon suboxide, substituted malonyl dichlorides, and ethy (chlorocarbonyllacetate. The thiazinium betaines were often isolable, and in one instance, a single-crystal X-ray characterization was possible. Cycloaddition of the thiazinium betaines occurred in a regiospecific manner. The initially formed cycloadducts which retained the carbonyl sulfide bridge could be induced to lose COS on further heating. Julolidine-type derivatives were obtained principally via a nonconcerted process. Variation in lactam ring size, coupled with tether length and substituent in the 1,3-bielectrophile, enabled control of ring size, substituents, and whether an ortho- orperi-fused tricyclic system resulted from the overall cycloaddition. In contrast to the lactam system, the thiolactams require disubstitution in the 3-position to avoid proton loss in the intermediate betaine with formation of a 1,3-thiazoline- 4,6-dione.
Περιγραφή
Λέξεις-κλειδιά
Θεματική κατηγορία
Παραπομπή
Σύνδεσμος
http://pubs.acs.org/doi/abs/10.1021/jo00117a035
Γλώσσα
en
Εκδίδον τμήμα/τομέας
Όνομα επιβλέποντος
Εξεταστική επιτροπή
Γενική Περιγραφή / Σχόλια
Ίδρυμα και Σχολή/Τμήμα του υποβάλλοντος
Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας