TY - JOUR

T1 - Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

AU - Rostovskii, N.V.

AU - Novikov, M.S.

AU - Khlebnikov, A.F.

AU - Starova, G.L.

AU - Avdontseva, M.S.

PY - 2015

Y1 - 2015

N2 - Strained azirinium ylides derived from 2H-azirines and alpha-diazoketones under Rh(II)-catalysis can undergo either irreversible ring opening across the N-C2 bond to 2-azabuta-1,3-dienes that further cyclize to 2H-1,4-oxazines or reversibly undergo a 1,5-cyclization to dihydroazireno[2,1-b] oxazoles. Dihydroazireno[2,1-b] oxazoles derived from 3-aryl-2H-azirines and 3-diazoacetylacetone or ethyl diazoacetoacetate are able to cycloadd to acetyl(methyl) ketene generated from 3-diazoacetylacetone under Rh(II) catalysis to give 4,6-dioxa-1-azabicyclo[3.2.1] oct-2-ene and/or 5,7-dioxa-1-azabicyclo[4.3.1] deca-3,8-diene-2-one derivatives. According to DFT calculations (B3LYP/6-31+ G(d, p)), the cycloaddition can involve two modes of nucleophilic attack of the dihydroazireno[2,1-b] oxazole intermediate on acetyl(methyl) ketene followed by aziridine ring opening into atropoisomeric oxazolium betaines and cyclization. Azirinium ylides generated from 2,3-di- and 2,2,3-triaryl-substituted azirines give rise to only 2-az

AB - Strained azirinium ylides derived from 2H-azirines and alpha-diazoketones under Rh(II)-catalysis can undergo either irreversible ring opening across the N-C2 bond to 2-azabuta-1,3-dienes that further cyclize to 2H-1,4-oxazines or reversibly undergo a 1,5-cyclization to dihydroazireno[2,1-b] oxazoles. Dihydroazireno[2,1-b] oxazoles derived from 3-aryl-2H-azirines and 3-diazoacetylacetone or ethyl diazoacetoacetate are able to cycloadd to acetyl(methyl) ketene generated from 3-diazoacetylacetone under Rh(II) catalysis to give 4,6-dioxa-1-azabicyclo[3.2.1] oct-2-ene and/or 5,7-dioxa-1-azabicyclo[4.3.1] deca-3,8-diene-2-one derivatives. According to DFT calculations (B3LYP/6-31+ G(d, p)), the cycloaddition can involve two modes of nucleophilic attack of the dihydroazireno[2,1-b] oxazole intermediate on acetyl(methyl) ketene followed by aziridine ring opening into atropoisomeric oxazolium betaines and cyclization. Azirinium ylides generated from 2,3-di- and 2,2,3-triaryl-substituted azirines give rise to only 2-az

U2 - 10.3762/bjoc.11.35

DO - 10.3762/bjoc.11.35

M3 - Article

VL - 11

SP - 302

EP - 312

JO - Beilstein Journal of Organic Chemistry

JF - Beilstein Journal of Organic Chemistry

SN - 1860-5397

ER -