Development of a flow photochemical process for a π-Lewis acidic metal-catalyzed cyclization/radical addition sequence: in situ-generated 2-benzopyrylium as photoredox catalyst and reactive intermediate

• Masahiro Terada,
• Zen Iwasaki,
• Ryohei Yazaki,
• Shigenobu Umemiya and
• Jun Kikuchi

Beilstein J. Org. Chem. 2024, 20, 1973–1980, doi:10.3762/bjoc.20.173

• benzyltrimethylsilane derivatives as the donor molecule in the flow photoreactor to provide 1H-isochromene derivatives in higher yields in most cases than the batch reaction system. Keywords: 2-benzopyrylium; flow chemistry; isocromene; photochemical reaction; π-Lewis acidic metal; Introduction Flow chemistry has

• subsequent photochemical radical addition [46][47][48][49][50][51][52][53][54], which affords 1H-isochromene derivatives 3 through three catalytic cycles (Scheme 1a) [55]: catalytic cycles I and II and a photoredox cycle of the photocatalyst [56][57] (see Supporting Information File 1 for the overall

• II is completed through a SET from D, a reduced form of the photoredox catalyst 2-benzopyrylium intermediates A, to the generated radical cation, affording 1H-isochromene derivatives 3. The photoredox cycle is also completed with the regeneration of cations A through SET from D. The most distinctive

Sequential Au(I)-catalyzed reaction of water with o-acetylenyl-substituted phenyldiazoacetates

• Lei Zhou,
• Yizhou Liu,
• Yan Zhang and
• Jianbo Wang

Beilstein J. Org. Chem. 2011, 7, 631–637, doi:10.3762/bjoc.7.74

• )-catalyzed reaction of water with o-acetylenyl-substituted phenyldiazoacetates provides 1H-isochromene derivatives in good yields. The reaction follows a catalytic sequence of gold carbene formation/water O–H insertion/alcohol-alkyne cyclization. The gold(I) complex is the only catalyst in each of these

• steps. Keywords: alkyne; carbene O–H insertion; cyclization; diazo compounds; gold catalysis; 1H-isochromene; Introduction Transition metal carbene complexes are versatile intermediates and can undergo diverse transformations, including X–H (X = C, O, S, N, etc.) insertions, cyclopropanations, ylide

• /cyclization cascade by reacting water with o-acetylenyl-substituted phenyldiazoacetates. The reaction affords 1H-isochromene derivatives in good yields (Scheme 1) [31]. Results and Discussion At the onset of this investigation, o-acetylenyl-substituted phenyldiazoacetate 1a was selected as the model substrate