Reactivity of Fully Conjugated Rings

In this section, the majority of new reactions are devoted to a continuation of the Appel salt chemistry, and its keto, thio, and ylidene derivatives, but imino-l,2,3-dithiazoles have attracted special attention by the Rees group. 

An electrochemical reaction on the azepine carbamates 19 resulted in a ring contraction to give the N-substituted anilines 20 in moderate yield (Equation 1). Mechanistically, initial oxidation of the carbamate to give the radical cation 21, followed by electrocyclic rearrangement to 22, C-N cleavage, and then reduction was proposed 1998H(48)1151 . 

Reaction of the 3//-azcpincs 23 (R = R2 = Buc, R1 = R3 = H) and 23 (R = R2 = H, R1 = R3 = Buc) with bromine and quenching with MeOH afforded the respective 2-methoxy-2//-azepine derivatives, which formed the more stable 3//-tautomers at 25 °G. In the latter, tautomerization proceeded further to produce the stable 2-azabicyclo[4.1.0]-heptadiene analogue 24 1997J(P1)2015 . The 3//-azepines 25 with a 2-methoxy, 2-amino, or 2-dimethylamino substituent underwent valence tautomerization under UV light irradiation to give 3-substituted 2-azabicyclo[3.2.0]-hepta-2,6-dienes 26 (Equation 2) 1997JCM276 no 5-substituted derivatives were observed. 

A photo-induced [6+2] cycloaddition of the chiral acrylate 28 with the chromium carbonyl complex 27 afforded the endo- AAuct 29 in high diastereomeric excess (Equation 3) 1995JOC7392 . 

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Synthesis and Reactivity of Fully Conjugated Rings Containing Phosphorus 531... 

Reactivity of Fully Conjugated Rings 12.18.4.1 Electrophilic Attack at Nitrogen... 

Reactivity of Fully Conjugated Rings 5.05.4.1 Furazans and Benzofurazans... 

Reactivity of Fully Conjugated Rings 11.05.5.1 Diels-Alder Reaction... 

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