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

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• the alkoxy group which can finally reductively eliminate the isochromene product. Based on control reactions, the authors proposed the active catalytic species is cationic, as the use of the cationic precatalyst [Cp*Ru(CH3CN)3]PF6 in THF afforded the isochromene as the major product, suggesting a

• cationic active ruthenium species, the authors noted the use of [Cp*Ru(CH3CN)3]PF6 as the precatalyst produced the cyclopropanated bicyclic alkene adducts exclusively. This contrasts with Tam’s report (Scheme 18) [55] which found cationic Ru species formed the isochromene 100 preferentially which may be

Synthesis of odorants in flow and their applications in perfumery

• Merlin Kleoff,
• Paul Kiler and
• Philipp Heretsch

Beilstein J. Org. Chem. 2022, 18, 754–768, doi:10.3762/bjoc.18.76

• ]isochromene), fruity (e.g., Helvetolide, 2-(1-(3,3-dimethylcyclohexyl)ethoxy)-2-methylpropyl propionate, has a distinct pear note), powdery (e.g., Tonalide, 1-(5,6,7,8-tetrahydro-3,5,5,6,8,8-hexamethyl-2-naphthalinyl)ethanone), or show even unexpected notes, such as a metallic character reminiscent of hot

New furoisocoumarins and isocoumarins from the mangrove endophytic fungus Aspergillus sp. 085242

• Ze’en Xiao,
• Senhua Chen,
• Runlin Cai,
• Shao’e Lin,
• Kui Hong and
• Zhigang She

Beilstein J. Org. Chem. 2016, 12, 2077–2085, doi:10.3762/bjoc.12.196

• to the chemical shifts of C-2 (δC 145.7) and C-9b (δC 165.1) as well as the required degrees of unsaturation. Thus, the structure of 1 was identified as 7-methyl-2-(propan-2-ylidene)-9H-furo[3,2-h]isochromene-3,9(2H)-dione, named asperisocoumarin A. Compound 2 was obtained as colorless crystals, and

• -dihydro-9H-furo[3,2-h]isochromen-9-one and (R)-7-methyl-2-(propan-2-ylidene)-6,7-dihydro-9H-furo[3,2-h]isochromene-3,9-(2H)-dione, respectively. Both have been synthesized as intermediates during synthesis and structural characterization of natural benzofuranoids [9]. Asperisocoumarin E (5) containing an

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• 72 with the NHC precatalyst 73 alone, on the other hand, afforded isochromeno(4,3-c)isochromene derivatives 75 (Scheme 44) [61]. A one-pot multicatalytic reaction for the asymmetric synthesis of complex tetracyclic tetrahydrocarbazole derivatives from readily available precursors was described by

Allenylphosphine oxides as simple scaffolds for phosphinoylindoles and phosphinoylisocoumarins

• G. Gangadhararao,
• Ramesh Kotikalapudi,
• M. Nagarjuna Reddy and
• K. C. Kumara Swamy

Beilstein J. Org. Chem. 2014, 10, 996–1005, doi:10.3762/bjoc.10.99

• parentheses: O2–C8 1.377(6), C8–C10 1.492(6). Reaction of P(III)-Cl precursors with propargyl alcohols leading to phosphorus based (a) N-hydroxyindolinone, (b) benzazepine, (c) indenone and (d) isochromene via allenic intermediates. Synthesis of functionalized allenes 3a–c, 3m and 4a–j. Reaction of

Synthesis and spectroscopic properties of 4-amino-1,8-naphthalimide derivatives involving the carboxylic group: a new molecular probe for ZnO nanoparticles with unusual fluorescence features

• Laura Bekere,
• David Gachet,
• Vladimir Lokshin,
• Wladimir Marine and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2013, 9, 1311–1318, doi:10.3762/bjoc.9.147

• , 1H), 8.07 (d, J = 8.5 Hz, 2H), 8.40 (d, J = 8.1 Hz, 1H), 8.47 (d, J = 8.4 Hz, 1H), 8.48 (d, J = 8.1, 1H), 13.00 (br s, COOH); Anal. calcd for C24H20N2O4: C, 71.99; H, 5.03; N, 7.00; found: C, 71.41; H, 5.10; N, 6.89. 6-(Piperidin-1-yl)-1H,3H-benzo[de]isochromene-1,3-dione (5): Preparation according

Synthesis of a novel chemotype via sequential metal-catalyzed cycloisomerizations

• Bo Leng,
• Stephanie Chichetti,
• Shun Su,
• Aaron B. Beeler and
• John A. Porco Jr.

Beilstein J. Org. Chem. 2012, 8, 1338–1343, doi:10.3762/bjoc.8.153

• cycloisomerizations of diynyl o-benzaldehyde substrates to access novel polycyclic cyclopropanes are reported. The reaction sequence involves initial Cu(I)-mediated cycloisomerization/nucleophilic addition to an isochromene followed by diastereoselective Pt(II)-catalyzed enyne cycloisomerization. Keywords: chemical

• diversity; cycloisomerization; cyclopropane; diyne; isochromene; π-acid; Introduction Our laboratory has an ongoing interest in discovering transformations that afford novel chemotypes [1][2][3][4]. To this end, we have developed a reaction screening paradigm that enables the discovery of new reaction

• processes and chemotypes [5]. For example, we have conducted multidimensional reaction screens using alkynyl o-benzaldehyde scaffolds, which revealed a number of reactions affording novel polycyclic scaffolds, including Au(III)-catalyzed addition of diethyl malonate to 1 to afford isochromene 2 (Scheme 1

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• nucleophiles to allenes, the addition of oxygen nucleophiles requires the use of chiral anions 384 (Scheme 62). Gold(I)-catalyzed asymmetric cyclization of 1,3-dihydroxymethyl-2-alkynylbenzene chromium complexes 389 gave planar chiral isochromene–chromium complexes 390 with high enantioselectivity [179

• ]. Enantioselectivities of the cyclized isochromene–chromium complexes are largely dependent on the combination of gold pre-catalysts and silver salts. The use of AgSbF6 resulted in excellent enantioselectivities, regardless of the nature of the gold pre-catalyst (Scheme 63). Julolidine derivatives 396 were obtained via

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