“…To replace the benzotriazolyl group with hydrogen, derivatives 397 are treated with zinc in refluxing acetic acid <1997JOC6215> . Similar benzotriazole-assisted side-chain transformations are reported for benzene <1997JOC721> , pyrrole 1996JOC1624 , 1996TL5641 , and indole 1995JOC3401 , 1995SC539 , 1996JOC7558 . Scheme 64 …”
Section: Reactivity Of Substituents Attached To Ring Nitrogenssupporting
“…To replace the benzotriazolyl group with hydrogen, derivatives 397 are treated with zinc in refluxing acetic acid <1997JOC6215> . Similar benzotriazole-assisted side-chain transformations are reported for benzene <1997JOC721> , pyrrole 1996JOC1624 , 1996TL5641 , and indole 1995JOC3401 , 1995SC539 , 1996JOC7558 . Scheme 64 …”
Section: Reactivity Of Substituents Attached To Ring Nitrogenssupporting
“…Synthesis of Substituted Carbazoles. The requisite 1-methyl-3-(benzotriazol-1-ylmethyl)indole ( 1 ) was readily prepared from 1-methylindole and 1-(hydroxymethyl)benzotriazole as described in our earlier work , compound 1 can be easily deprotonated at the side-chain CH 2 group.…”
Section: Resultsmentioning
confidence: 99%
“…1-Methyl-3-(benzotriazol-1-ylmethyl)indole (1) was prepared according to our previously reported procedure. 17 General Procedure for the Preparation of Substituted Carbazoles 6a-j and 8. To a solution of 1-methyl-3-(benzotriazol-1-ylmethyl)indole (1) (1.05 g, 4 mmol) in THF (75 mL) at -78 °C under argon was added n-BuLi (1.7 mL, 2.5 M in hexane, 4.4 mmol).…”
Section: Methodsmentioning
confidence: 99%
“…Our recent work has demonstrated the versatility of benzotriazolylalkyl-substituted heterocycles for the synthesis of 1,1-bis(heteroaryl)alkanes and the utility of 1-methyl-3-(benzotriazol-1-ylmethyl)indole ( 1 ) for the synthesis of a wide range of 3-substituted indoles and heterocyclo[ b ]-fused carbazoles . The chemistry of compound 1 has now been further developed to provide facile and efficient routes to substituted carbazoles and cyclopenta[ b ]indoles.…”
1-Methyl-3-(benzotriazol-1-ylmethyl)indole (1) undergoes lithiation and 1,4-addition with a variety of alpha,beta-unsaturated ketones and aldehydes. Subsequent treatment with an acidic resin in refluxing 1,4-dioxane causes intramolecular cyclization followed by aromatization to furnish a wide range of 1,3-di-, 2,3-di-, and 1,2,3-trisubstituted carbazoles 6a-j and 8 in moderate to excellent yields. NMR study is described to discriminate between structures of types 6 and 8 on the basis of (1)H-(13)C long-range correlation. Treatment of 1 with styrenes in the presence of zinc bromide results in formal [3 + 2] cycloaddition to give cyclopent[b]indoles 14a-c in good yields. When 1 is first lithiated and reacts with electrophiles, the resulting alkylation products undergo similar [3 + 2] additions with styrenes to give 1-functionalized cyclopent[b]indoles 15 and 16with a high degree of stereoselectivity.
“…Preparation of the Starting Materials. Compounds 1a,b , 1c , 1e , 1f , 1g , 1h , 5a , and 5b 17 were prepared by the literature methods quoted. Compounds 5c,d were obtained by the reaction of benzotriazole with the corresponding allyl halide in the presence of sodium hydroxide in ethanol by analogy to the literature .…”
Lithiation with n-butyllithium of a variety of benzotriazole derivatives 1a
−
f and 5a
−
d, all
containing a proton α to the benzotriazolyl moiety, gave anions which underwent addition to
aliphatic, aromatic, and α,β-unsaturated aldehydes and cyclic and acyclic ketones. The resultant
N-(β-hydroxyalkyl)benzotriazole derivatives 3a
−
m, 6a
−
g, 9a
−
d, and 10a were dehydroxybenzotriazolylated when treated with low-valent titanium to give alkenes 4a
−
m, dienes 7a
−
j, and triene
11a, with selectivity for the trans isomers without separation of diastereoisomeric intermediates.
This method offers an alternative to the three most frequently used methods for the formation of
alkenes from carbonyl compoundsthe Wittig, Peterson, and Julia reactionsespecially in the
formation of tri- and tetrasubstituted alkenes.
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