Trig

The principle of the acquisition system is to translate the probe into a tube (including hemispherical drilled holes) step by step, every 0.04 mm, after a forwards and backwards 360 rotation of the tube trigging every 0.2° angular step a 360° electronic scanning of tube with the 160 acoustic apertures. During the electronic scanning the tube is assumed to stay at the same place. The acquisition lasts about 30 minutes for a C-scan acquisition with a 14 kHz recurrence frequency. 

Endo-Trig, 4-Endo-Trig and 5-Endo-Trig are disfavored 6-Endo-Trig, 7-Endo-Trig, etc. are favored... 

Both the 5-exo-trig and 6-endo trip are favored reactions, with the 6 exo-trig mode producing the most stable radical. However, the 5-exo-trig is about 50 time faster... 

Intramolecular AAcM Condensation of 1,5-Diketones 6-exo-trig favored process... 

The dienyne 394 undergoes facile polycyclization. Since the neopentylpalla-dium 395 is formed which has no hydrogen /J to the Pd after the insertion of the disubstituted terminal alkene, the cyclopropanation takes place to form the tt-allylpalladium intermediate 396, which is terminated by elimination to form the diene 397(275]. The dienyne 398 undergoes remarkable tandem 6-e. o-dig. 5-cxo-trig. and -exo-trig cyclizations to give the tetracycle 399 exclu-sively(277]. 

Rctrosynthetic path a corresponds to Pd-catalysed exo-trig cyclization of o-halo-JV-allylanilines. Path b involves the endo-trig cyclization of o-halo-JV-vinyl anilines. Path c is a structurally similar cyclization which can be effected photochemically in the absence of an o-substituent. Retrosynthetic path d involves intramolecular Friedel-Crafts oxyalkylation followed by aromatiz-ation. 

Besides Pd-catalysed cyclizations, both radical[12] and organolithium[13] intermediates can give oxindoles by exo-trig additions. 

P. Duwez, in R. G. Lemer and G. L. Trig, eds. Concise Encyclopedia of Solid State Phjsics Addison-Wesley, Reading, Mass., 1983, p. 112. 

As foretold in the introduction, ring formation via attack on a double bond in the endo-trig mode is not well exemplified. The palladium(II) catalyzed oxidative cyclization of o-aminostyrenes to indoles has been described (78JA5800). The treatment of o-methyl-selenocinnamates with bromine in pyridine gives excellent yields of benzoselenophene-2-carboxylates (Scheme 10a) (77BSF157). The base promoted conversion of dienoic thioamides to 2-aminothiophenes is another synthetically useful example of this type (Scheme 10b) (73RTC1331). 

---