Generation and Trapping of Ketenes in Flow

Abstract

Ketenes were generated by the thermolysis of alkoxyalkynes under flow conditions, and then trapped with amines and alcohols to cleanly give amides and esters. For a 10 min reaction time, temperatures of 180, 160, and 140 °C were required for >95 % conversion of EtO, iPrO, and tBuO alkoxyalkynes, respectively. Variation of the temperature and flow rate with inline monitoring of the output by IR spectroscopy allowed the kinetic parameters for the conversion of 1-ethoxy-1-octyne to be easily estimated (Ea = 105.4 kJ/mol). Trapping of the in-situ-generated ketenes by alcohols to give esters required the addition of a tertiary amine catalyst to prevent competitive [2+2] addition of the ketene to the alkoxyalkyne precursor.

Metal-Free Transamidation of Secondary Amides by N–C Cleavage

“…Amides 3a , 3b , 3c , 3d , 3e , 3f , 3h , 3i , 3j , 3k , 3l , 3m , 3n , 3o , 3p , 3q , 3r , 3s , 3t , 3u , 3v , 3w , 3x , 3y , and 4 have been previously reported. Spectroscopic data match those reported in the literature.…”

Cobalt(II)‐Catalyzed N‐Acylation of Amines through a Transamidation Reaction

“…N ‐Acetyl‐1,2,3,4‐tetrahydroisoquinoline (2za): Purified by TLC to give 2za (94 %) as a yellow oil. 1 H NMR (400 MHz, CDCl 3 ): δ = 7.20–7.13 (m, 4 H), 4.72 (major rotamer, s, 1.15 H), 4.61 (minor rotamer, 0.85 H), 3.81 (minor rotamer, t, J = 6.0 Hz, 0.85 H), 3.67 (major rotamer, t, J = 6.0 Hz, 1.12 H), 2.91 (major rotamer, t, J = 5.8 Hz, 1.17 H), 2.85 (minor rotamer, t, J = 6.0 Hz, 0.82 H), 2.18 (minor rotamer, s, 1.42 H), 2.17 (major rotamer, s, 1.61 H) ppm.…”

Mn(II)-Catalyzed N-Acylation of Amines

“…IR (neat): 3140, 3006, 2941IR (neat): 3140, 3006, , 1668IR (neat): 3140, 3006, , 1593IR (neat): 3140, 3006, , 1467IR (neat): 3140, 3006, , 1400IR (neat): 3140, 3006, , 1265, 1029 cm -1 . Acetyl-1,2,3,4-tetrahydroisoquinoline (2z) 34 Purified by TLC; yellow oil; yield: 30.1 mg (86%). IR (neat): 3159, 3029, 2933IR (neat): 3159, 3029, , 1661IR (neat): 3159, 3029, , 1634IR (neat): 3159, 3029, , 1456IR (neat): 3159, 3029, , 1403IR (neat): 3159, 3029, , 1299IR (neat): 3159, 3029, , 1034 .…”