[2,3] Sigmatropic rearrangement of 1-vinylic tetrahydroisoquinoline N-ylides and N-oxides.

Diversity-oriented synthetic strategy for developing a chemical modulator of protein–protein interaction

“…4). Oxidation of SI – 7 with 3-chloroperbenzoic acid ( m -CPBA) and conversion of seven-membered ring into 10-membered ring via in situ [2,3]-sigmatropic ring expansion of the resultant N -oxide provided 13f (scaffold V ) with excellent (E) -selectivity (Supplementary Figs 4 and 12)30.…”

Synthesis and X-ray Structural Studies of a Substituted 2,3,4,5-Tetrahydro-1H-3-benzazonine and a 1,2,3,5-Tetrahydro-4,3-benzoxazonine

“…On the other hand, with the corresponding trans-isomeric ylide or N-oxide, this is not the case, and the diradical mediated [1,2] rearrangements to give seven-membered ring products can then proceed. Interestingly, with a 1-ethenyl or 1-isopropenyl substituent in the tetrahydroisoquinoline precursor of the corresponding ylide, only the Stevens [2,3] rearrangement products were observed, while the analogous N-oxides gave only the Meisenheimer [1,2] rearrangement product (from the 1-ethenyl precursor) or a mixture of the [1,2] and [2,3] rearrangement products (from the 1-isopropenyl precursor) on heating at reflux in acetonitrile for 50 min [17].…”

“…Synthetic approaches to these systems often involve rearrangement strategies incorporating a ring expansion [8][9][10][11], although ring formation [12][13][14] and ring cleavage approaches [5,15,16] can also be used. The Meisenheimer [1,2] and [2,3] sigmatropic rearrangements of amine N-oxides [17][18][19] and the analogous Stevens [2,3] sigmatropic rearrangements of ylides [20,21] afford good opportunities for medium ring synthesis. To further explore these synthetic prospects and to assess substituent effects (e.g., a phenyl group vs. a methyl group or hydrogen [17]) on configurational and conformational issues in the products, we have investigated the synthetic utility of the [2,3] versions of these rearrangements from the same starting amine precursor, the 1-(1-phenylethenyl) substituted tetrahydroisoquinoline derivative 3.…”

“…The Meisenheimer [1,2] and [2,3] sigmatropic rearrangements of amine N-oxides [17][18][19] and the analogous Stevens [2,3] sigmatropic rearrangements of ylides [20,21] afford good opportunities for medium ring synthesis. To further explore these synthetic prospects and to assess substituent effects (e.g., a phenyl group vs. a methyl group or hydrogen [17]) on configurational and conformational issues in the products, we have investigated the synthetic utility of the [2,3] versions of these rearrangements from the same starting amine precursor, the 1-(1-phenylethenyl) substituted tetrahydroisoquinoline derivative 3. These rearrangements involve three-atom ring expansions with incorporation of an O-C-C (Meisenheimer) or C-C-C (Stevens) unit into the six-membered N-containing ring.…”