[3 + 3]-Cycloaddition Reactions of α-Acidic Isocyanides with 1,3-Dipolar Azomethine Imines

Abstract

α-Acidic isocyanides are versatile reagents in organic synthesis, especially for the synthesis of five-membered heterocycles via [3 + 2]-cycloaddition reactions with activated multiple bonds. In this communication, the first [3 + 3]-cross-cycloaddition of α-acidic isocyanides with 1,3-dipolar azomethine imines to generate a series of 1,2,4-triazine derivatives with significant regiochemical control under mild catalytic reaction conditions is described. This new strategy shows that α-acidic isocyanides can also be taken as potent reagents for the synthesis of six-membered heterocycles through [3 + 3]-cross-cycloaddition reactions with 1,3-dipoles.

1,3-Dipolar cycloadditions of azomethine imines

“…124 Isocyanides 209 and azomethine imines 169 gave a [3+3] cycloaddition to give pyrazole[1,2-a]triazin-8(4H)-ones 210 (Scheme 81). 125 The process takes place with high stereocontrol using CuI as catalyst and DBU as base at room temperature. Silver salts and other copper salts provided lower yield than CuI.…”

Silver‐Catalyzed Chemoselective [4+2] Annulation of Two Isocyanides: A General Route to Pyridone‐Fused Carbo‐ and Heterocycles

“…During the past decade, isocyanide‐based cycloaddition has been well developed and shown to be one of the most powerful strategies for the synthesis of diverse classes of heterocycles . These reactions mainly involve the participation of activated methylene isocyanides (as a three‐atom component) in [3+2], [3+3], and [3+6] annulations and of isocyanides (as a one‐atom component) in [1+4], [1+5], and [1+2+2] annulations . Among these transformations, the [3+2] cycloaddition of activated methylene isocyanides with aryl isocyanides has emerged as an efficient protocol for the catalytic synthesis of imidazoles [Scheme , Eq.…”

Silver‐Catalyzed Chemoselective [4+2] Annulation of Two Isocyanides: A General Route to Pyridone‐Fused Carbo‐ and Heterocycles

“…[1][2][3][4][5][6][7][8] These reactions mainly involve the participation of activated methylene isocyanides (as at hree-atom component) in [3+ +2], [3] [3+ +3], [4] and [3+ +6] annulations [5] and of isocyanides (as ao ne-atom component) in [1+ +4], [2,6] [1+ +5], [7] and [1+ +2+ +2] annulations. [1][2][3][4][5][6][7][8] These reactions mainly involve the participation of activated methylene isocyanides (as at hree-atom component) in [3+ +2], [3] [3+ +3], [4] and [3+ +6] annulations [5] and of isocyanides (as ao ne-atom component) in [1+ +4], [2,6] [1+ +5], [7] and [1+ +2+ +2] annulations.…”

“…

Asilver-catalyzed chemoselective [4+ +2] annulation of aryl and heteroaryl isocyanides with a-substituted isocyanoacetamides was developed for the facile and efficient synthesis of 2-aminoquinolones,n aphthyridines,a nd phenanthrolines.Amechanism for this multistep domino reaction is proposed on the basis of a 13 C-labeling experiment, according to whichanunprecedented chemoselective heterodimerization of two different isocyanides generates an a-amidoketenimine intermediate,whichundergoes 1,3-amino migration to form an a-imidoylketene,followed by 6 p electrocyclization.During the past decade,isocyanide-based cycloaddition has been well developed and shown to be one of the most powerful strategies for the synthesis of diverse classes of heterocycles. [1][2][3][4][5][6][7][8] These reactions mainly involve the participation of activated methylene isocyanides (as at hree-atom component) in [3+ +2], [3] [3+ +3], [4] and [3+ +6] annulations [5] and of isocyanides (as ao ne-atom component) in [1+ +4], [2,6] [1+ +5], [7] and [1+ +2+ +2] annulations. [8] Among these transformations,t he [3+ +2] cycloaddition of activated methylene isocyanides with aryl isocyanides has emerged as an efficient protocol for the catalytic synthesis of imidazoles [Scheme 1, Eq.

…”

“…During the past decade,isocyanide-based cycloaddition has been well developed and shown to be one of the most powerful strategies for the synthesis of diverse classes of heterocycles. [1][2][3][4][5][6][7][8] These reactions mainly involve the participation of activated methylene isocyanides (as at hree-atom component) in [3+ +2], [3] [3+ +3], [4] and [3+ +6] annulations [5] and of isocyanides (as ao ne-atom component) in [1+ +4], [2,6] [1+ +5], [7] and [1+ +2+ +2] annulations. [8] Among these transformations,t he [3+ +2] cycloaddition of activated methylene isocyanides with aryl isocyanides has emerged as an efficient protocol for the catalytic synthesis of imidazoles [Scheme 1, Eq.…”