Synthesis of Diazoquinones and Azidophenols via Diazo‐Transfer Reaction of Phenols

Abstract

Dedicated to Professor Koichi Narasaka with Gratitude on the occasion of his 77th Birthday (Kiju).The first efficient diazo-transfer reaction of phenols is described. o-Quinone diazides (diazoquinones) were prepared from phenols in high yields by the diazo-transfer reaction using 2-azido-1,3-bis(2,6-diisopropylphenyl)imidazolium hexafluorophosphate (IPrAP, 2-PF 6 ), which is a safe and stable crystalline. The reaction efficiently proceeded in methanol in the presence of a base. Phenols substituted with electron-donating groups reacted more smoothly than those having electron withdrawing groups. Reactive phenols were diazotized by IPrAP with i Pr 2 NH as a base, and low reactive phenols were diazotized with N,Ndimethyl-4-aminopyridine (DMAP). Furthermore, the formed diazoquinones reacted with sodium azide in 2-methoxyethanol and afforded the corresponding azidophenol in high yields.

Synthesis of Bench‐stable Polycyclic Organophosphorus Heterocycles via Staudinger‐type Annulations of ortho‐Azidophenols

“…Both O1 and C2 occupy the axial positions and the bond angle of O1À P1À C2 is 172.30(15)°. In addition, the bond angle of N1À P1À C5, N1À P1À C6, and C5À P1À C6 are 122.00(16)°, 122.11(17)°, and 115.24 (17), respectively. The bond length of P1À N1 is 1.745(3) Å, shorter than the ones of P1À C5 and P1À C6 bonds.…”

“…The authors have cited additional references within the Supporting Information. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]…”

Diazo-Transfer Reaction of Nonactivated Ketones with 2-Azido-1,3-bis(2,6-diisopropylphenyl)imidazolium Hexafluorophosphate (IPrAP)

“…Pyridine and triethylamine were distilled from KOH and stored over KOH. 2-Azido-1,3-bis­(2,6-diisopropylphenyl)­imidazolium hexafluorophosphate (IPrAP) was prepared following our procedure . 4-Acetamidobenzenesulfonyl azide was purchased from Tokyo Chemical Industry Co. Ltd. and was used as received.…”

“…Sulfonyl azides used as diazo-transfer reagents and the product diazo compounds are potentially explosive . IPrAP has been found to be safe in friction and impact sensitivity tests . However, the safety of IPrAP has not been confirmed when it has been left for long periods of time, such as more than one year.…”

“…Since we found that azidoimidazolinum salts are efficient diazo-transfer reagents, we have been studying the reaction of the azidoimidazolinum salts . Recently, we developed a new nonexplosive diazo-transfer reagent, 2-azido-1,3-bis­(2,6-diisopropylphenyl)­imidazolium hexafluorophosphate (IPrAP), which enabled the diazo-transfer reaction to afford a simple phenol for the first time (Scheme , eq 1) . The result suggested that IPrAP could diazotize relatively weakly nucleophilic compounds.…”