Research output: Contribution to journal › Article
Pseudopericyclic 1,5- versus pericyclic 1,4- and 1,6-electrocyclization in electron-poor 4-aryl-2-azabuta-1,3-dienes. Indole synthesis from 2H-azirines and diazo compounds. / Novikov, Mikhail S.; Khlebnikov, Alexander F.; Rostovskii, Nikolai V.; Tcyrulnikov, Sergei; Suhanova, Anna A.; Zavyalov, Kirill V.; Yufit, Dmitry S.
In: Journal of Organic Chemistry, Vol. 80, No. 1, 2015, p. 18-29.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Pseudopericyclic 1,5- versus pericyclic 1,4- and 1,6-electrocyclization in electron-poor 4-aryl-2-azabuta-1,3-dienes. Indole synthesis from 2H-azirines and diazo compounds
AU - Novikov, Mikhail S.
AU - Khlebnikov, Alexander F.
AU - Rostovskii, Nikolai V.
AU - Tcyrulnikov, Sergei
AU - Suhanova, Anna A.
AU - Zavyalov, Kirill V.
AU - Yufit, Dmitry S.
PY - 2015
Y1 - 2015
N2 - Transformations of 2-azabuta-1,3-dienes, formed in Rh2(OAc)4-catalyzed reactions of diazo carbonyl compounds with 2H-azirines, dramatically depend on the nature of substituents. 4,4-Diphenyl-2-azabuta-1,3-dienes with two electron-acceptor substituents at C(1) undergo thermal 1,5-cyclization to give indoles in good yields. The increase in electron-withdrawing ability of C(1)-substituents facilitates the reaction that proceeds via pseudopericyclic 1,5-electrocyclization of 2-azabutadiene into 7aH-indolium ylide followed by prototropic shift. 3,4-Diphenyl-2-azabuta-1,3-dienes, resulting from reaction of 2,3-diphenyl-2H-azirine and diazo compounds, do not produce indoles via 1,5-cyclization due to the trans-configuration of the 4-Ph-group and the nitrogen, but undergo 1,4-cyclization to 2,3-dihydroazetes. 1,6-Cyclization into 2H-1,4-oxazines with participation of the oxygen of ester or amide group at C(1) of corresponding 2-azabuta-1,3-dienes does not take place due to kinetic and thermodynamic reasons. Instead of this, 1,6-electrocyclization with participation of phenyl substituent at C(4) of the 2-azabuta-1,3-dienes, providing isoquinoline derivatives, can occur at elevated temperatures. The DFT-calculations (mPWB1K/6-31+G(d,p)) confirm the dependence of 2-azabuta-1,3-diene transformation type on the nature of substituents.
AB - Transformations of 2-azabuta-1,3-dienes, formed in Rh2(OAc)4-catalyzed reactions of diazo carbonyl compounds with 2H-azirines, dramatically depend on the nature of substituents. 4,4-Diphenyl-2-azabuta-1,3-dienes with two electron-acceptor substituents at C(1) undergo thermal 1,5-cyclization to give indoles in good yields. The increase in electron-withdrawing ability of C(1)-substituents facilitates the reaction that proceeds via pseudopericyclic 1,5-electrocyclization of 2-azabutadiene into 7aH-indolium ylide followed by prototropic shift. 3,4-Diphenyl-2-azabuta-1,3-dienes, resulting from reaction of 2,3-diphenyl-2H-azirine and diazo compounds, do not produce indoles via 1,5-cyclization due to the trans-configuration of the 4-Ph-group and the nitrogen, but undergo 1,4-cyclization to 2,3-dihydroazetes. 1,6-Cyclization into 2H-1,4-oxazines with participation of the oxygen of ester or amide group at C(1) of corresponding 2-azabuta-1,3-dienes does not take place due to kinetic and thermodynamic reasons. Instead of this, 1,6-electrocyclization with participation of phenyl substituent at C(4) of the 2-azabuta-1,3-dienes, providing isoquinoline derivatives, can occur at elevated temperatures. The DFT-calculations (mPWB1K/6-31+G(d,p)) confirm the dependence of 2-azabuta-1,3-diene transformation type on the nature of substituents.
U2 - 10.1021/jo501051n
DO - 10.1021/jo501051n
M3 - Article
VL - 80
SP - 18
EP - 29
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
SN - 0022-3263
IS - 1
ER -
ID: 3937256