132589-34-5Relevant academic research and scientific papers
Divergent Syntheses of Indoles and Quinolines Involving N1-C2-C3 Bond Formation through Two Distinct Pd Catalyses
San Jang, Su,Kim, Young Ho,Youn, So Won
supporting information, p. 9151 - 9157 (2020/11/03)
Pd-catalyzed annulative couplings of 2-alkenylanilines with aldehydes using alcohols as both the solvent and hydrogen source have been developed. These domino processes allow divergent syntheses of two significant N-heterocycles, indoles and quinolines, from the same substrate by tuning reaction parameters, which seems to invoke two distinct mechanisms. The nature of the ligand and alcoholic solvent had a profound influence on the selectivity and efficiency of these protocols. Particularly noteworthy is that indole formation was achieved by overcoming two significant challenges, regioselective hydropalladation of alkenes and subsequent reactions between the resulting Csp3-Pd species and less reactive imines.
140. Acid-Catalyzed -Sigmatropic Rearrangements of N-Propargylanilines
Barmettler, Peter,Hansen, Hans-Juergen
, p. 1515 - 1573 (2007/10/02)
The acid-catalyzed rearrangement of N-(1',1'-dimethylprop-2'-ynyl)-, N-(1'-methylprop-2'-ynyl)-, and N-(1'-arylprop-2'-ynyl)-2,6-, 2,4,6-, and 2,3,5,6-, and 2,3,4,5,6-substituted anilines in mixtures of 1N aqueous H2SO4 and ROH such as EtOH, PrOH, BuOH etc., or in CDCl3 or CCl4 in the presence of 4 to 9 mol-equiv. trifluoroacetic acid (TFA) has been investigated (cf.Scheme 12-25 and Tables 6 and 7).The rearrangement of N-(3'-X-1',1'-dimethyl-prop-2'-ynyl)-2,6- and 2,4,6-trimethylanilines (X = Cl, Br, I) in CDCl3/TFA occurs already at 20 deg C with τ1/2 of ca. 1 to 5 h to yield the corresponding 6-(1'-X-3'-methylbuta-1',2'-dienyl)-2,6-dimethyl- or 2,4,6-trimethylcyclohexa-2,4-dien-1-iminium ions (cf.Scheme 13 and Footnotes 26 and 34).When the 4 position is not substituted, a consecutive -sigmatropic rearrangement takes place to yield 2,6-dimethyl-4-(3'-X-1'1'-dimethylprop-2'-ynyl)anilines (cf.Footnotes 26 and 34).A comparable behavior is exhibited by N-(3'chloro-1'-phenylprop-2'-ynyl)-2,6-dimethylaniline (45; cf.Table 7).The acid-catalyzed rearrangement of the anilines with a Cl substituent at C(3') in 1N aqueous H2SO4/ROH at 85-95 deg C, in addition, leads to the formation of 7-chlorotricyclo2,7>oct-3-en-8-ones as the result of an intramolecular Diels-Alder reaction of the primarily formed iminium ions followed by hydrolysis of the iminium function (or vice versa; cf.Schemes 13, 23, and 25 as well as Table 7).When there is no X substituent at C(1') of the iminium-ion intermediate, a -sigmatropic shift of the allenyl moity at C(6) occurs in competition to the -sigmatropic rearrangement to yield the corresponding 3-allenyl-substituted anilines (cf.Schemes 12, 14-18, and 20 as well as Tables 6 and 7).The rearrangement of (-)-(S)-N-(1'phenylprop-2'-ynyl)-2,6-dimethylaniline ((-)-38; cf.Table 7) in a mixture of 1N H2SO4/PrOH at 86 deg C leads to the formation of (-)-(R)-3-(3'-phenylpropa-1',2'-dienyl)-2,6-dimethylaniline ((-)-91), (+)-(E)- and (-)-(Z)-6-benzylidene-1,5-dimethyltricyclo2,7>oct-3-en-8-one ((+)-(E)- and (-)-(Z)-92, respectively), and (-)-(S)-2,6-dimethyl-4-(1'-phenylprop-2'-ynyl)aniline ((-)-93).Recovered starting material (10percent) showed a loss of 18percent of its original optical purity.On the other hand, (+)-(E)- and (-)-(Z)-92 showed the same optical purity as (-)-38, as expected for intramolecular concerted processes.The CD of (+)-(E)- and (-)-(Z)-92 clearly showed that their tricyclic skeletons possess enantiomorphic structures (cf.Fig. 1).Similar results were obtained from the acid-catalyzed rearrangement of (-)-(S)-N-(3'-chloro-1'-phenylprop-2'-ynyl)-2,6-dimethylaniline ((-)-45; cf.Table 7).The recovered starting material exhibited in this case a loss of 48percent of its original optical purity, showing that the Cl substituent favors the heterolytic cleavage of the N-C(1') bond in (-)-45.A still higher degree (78percent) of loss of optical activity of the starting aniline ...
