N-Quaternized ketene N,O-acetals are typically an unstable, transient class of compounds most commonly observed as reactive intermediates. In this report, we describe a general synthetic approach to a variety of bench-stable N-quaternized ketene N,O-acetals via treatment of pyridine or aniline bases with acetylenic ethers and an appropriate Brønsted or Lewis acid (triflic acid, triflimide, or scandium(III) triflate). The resulting pyridinium and anilinium salts can be used as reagents or synthetic intermediates in multiple reaction types. For example, N-(1-ethoxyvinyl)pyridinium or anilinium salts can thermally release highly reactive O-ethyl ketenium ions for use in acid catalyst-free electrophilic aromatic substitutions. N-(1-Ethoxyvinyl)-2-halopyridinium salts can be employed in peptide couplings as a derivative of Mukaiyama reagents or react with amines in nucleophilic aromatic substitutions under mild conditions. These preliminary reactions illustrate the broad potential of these currently understudied compounds in organic synthesis.

N-Quaternized ketene N,O-acetals are typically an unstable, transient class of compounds most commonly observed as reactive intermediates. In this report, we describe a general synthetic approach to a variety of bench-stable N-quaternized ketene N,O-acetals via treatment of pyridine or aniline bases with acetylenic ethers and an appropriate Brønsted or Lewis acid (triflic acid, triflimide, or scandium(III) triflate). The resulting pyridinium and anilinium salts can be used as reagents or synthetic intermediates in multiple reaction types. For example, N-(1ethoxyvinyl)pyridinium or anilinium salts can thermally release highly reactive O-ethyl ketenium ions for use in acid catalyst-free electrophilic aromatic substitutions. N-(1-Ethoxyvinyl)-2-halopyridinium salts can be employed in peptide couplings as a derivative of Mukaiyama reagents or react with amines in nucleophilic aromatic substitutions under mild conditions. These preliminary reactions illustrate the broad potential of these currently understudied compounds in organic synthesis.

<div>N-Quaternized ketene N,O-acetals are typically an unstable, transient class of compounds most commonly observed as reactive intermediates. In this report, we describe a general approach to a variety of benchstable N-quaternized ketene N,O-acetals via treatment of pyridine or aniline bases with ethoxyacetylene and an appropriate Brønsted or Lewis acid (triflic acid, triflimide, or scandium(III) triflate). The resulting pyridinium and anilinium salts may be used as reagents or synthetic intermediates in multiple reaction types. For example, N-(1-ethoxyvinyl) pyridinium or anilinium salts can thermally release highly reactive O-ethyl ketenium ions that undergo electrophilic aromatic substitution with electron rich arenes. N-(1-ethoxyvinyl)-2-halopyridinium salts can also be utilized in peptide couplings as a derivative of Mukaiyama reagents, or react with alcohol and amines in nucleophilic aromatic substitutions.</div>

<div>N-Quaternized ketene N,O-acetals are typically an unstable, transient class of compounds most commonly observed as reactive intermediates. In this report, we describe a general approach to a variety of benchstable N-quaternized ketene N,O-acetals via treatment of pyridine or aniline bases with ethoxyacetylene and an appropriate Brønsted or Lewis acid (triflic acid, triflimide, or scandium(III) triflate). The resulting pyridinium and anilinium salts may be used as reagents or synthetic intermediates in multiple reaction types. For example, N-(1-ethoxyvinyl) pyridinium or anilinium salts can thermally release highly reactive O-ethyl ketenium ions that undergo electrophilic aromatic substitution with electron rich arenes. N-(1-ethoxyvinyl)-2-halopyridinium salts can also be utilized in peptide couplings as a derivative of Mukaiyama reagents, or react with alcohol and amines in nucleophilic aromatic substitutions.</div>

N-Quaternized ketene N,O-acetals are typically an unstable, transient class of compounds most commonly observed as reactive intermediates. In this report, we describe a general synthetic approach to a variety of bench-stable N-quaternized ketene N,O-acetals via treatment of pyridine or aniline bases with acetylenic ethers and an appropriate Brønsted or Lewis acid (triflic acid, triflimide, or scandium(III) triflate). The resulting pyridinium and anilinium salts can be used as reagents or synthetic intermediates in multiple reaction types. For example, N-(1-ethoxyvinyl)pyridinium or anilinium salts can thermally release highly reactive O-ethyl ketenium ions for use in acid catalyst-free electrophilic aromatic substitutions. N-(1-Ethoxyvinyl)-2-halopyridinium salts can be employed in peptide couplings as a derivative of Mukaiyama reagents or react with amines in nucleophilic aromatic substitutions under mild conditions. These preliminary reactions illustrate the broad potential of these currently understudied compounds in organic synthesis.