Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• necessary for achieving high reactivity, presumably because it minimizes undesired ligation of the benzoxazole substrates or intermediates. A variety of α-substituted acrylates as well as methacrylonitrile were good substrates. The system is sensitive to sterics, an acetate additive was needed to improve

• rhodium catalyst binding to the benzoxazole nitrogen 68. Deuterium labeling studies were performed on the system and based on their results a mechanism was proposed in which the stereodetermining step is a rhodium-hydride transfer instead of protonation of an oxo-π-allylrhodium species (Scheme 17

2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

• Yury A. Sayapin,
• Inna O. Tupaeva,
• Alexandra A. Kolodina,
• Eugeny A. Gusakov,
• Vitaly N. Komissarov,
• Igor V. Dorogan,
• Nadezhda I. Makarova,
• Anatoly V. Metelitsa,
• Valery V. Tkachev,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236

• (4,5,6,7-tetrachloro)-1,3-tropolones with alcohols leads to the contraction of the seven-membered tropone ring with the formation of 2-(2-benzoxa(thia)zolyl)-6-alkoxycarbonylphenols. The molecular structure of 2-(2-ethoxycarbonyl-6-hydroxy-3,4,5-trichlorophenyl)benzoxazole has been determined by X-ray

• -trichloro-1,3-tropolone, 2-(benzoxazolyl)-4,5,6,7-tetrachloro-1,3-tropolone, 2-(2-ethoxycarbonyl-3,4-dichloro-6-hydroxyphenyl)benzoxazole, 2-(2-ethoxycarbonyl-6-hydroxy-3,4,5-trichlorophenyl)benzoxazole, 2-(5-chlorobenzothiazolyl)-5,6,7-trichloro-1,3-tropolone and 2-(5-chlorobenzothiazolyl)-4,5,6,7

• )benzoxazole 11b is shown in Figure 4. All atoms of the benzoxazolyl fragment of 11b are located in a single plane with the accuracy of 0.005 Å. A common plane (with the accuracy of 0.02 Å) is formed by С(1), С(2), С(3), С(4), С(5), C(7), О(2) and two chlorine atoms Cl(1) and Cl(2). The torsion angle N(1)–С(8

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• 6 to form 7) [42], benzoxazole (acetoxylation of 8 to form 9) [43], benzimidazole (alkoxylation of 10 to form 11) [44], and triazole (acyloxylation of 12 to form 13 [45], alkoxylation of 14 to form 15 [46]) moieties were also used as directing groups for the ortho-acyloxylation and alkoxylation of

Palladium-catalyzed 2,5-diheteroarylation of 2,5-dibromothiophene derivatives

• Fatma Belkessam,
• Aidene Mohand,
• Jean-François Soulé,
• Abdelhamid Elias and
• Henri Doucet

Beilstein J. Org. Chem. 2014, 10, 2912–2919, doi:10.3762/bjoc.10.309

• et al. reported the Pd-catalyzed coupling of 2,5-dibromothiophene with 3-methoxythiophene to afford the corresponding terthiophene in 29% yield [37]. From 2,5-diiodothiophene and benzoxazole, using 5 mol % Pd(phen)2(PF6)2 catalyst, the 2,5-diheteroarylated thiophene was obtained in 89% yield by Murai

Amyloid-β probes: Review of structure–activity and brain-kinetics relationships

• Todd J. Eckroat,
• Abdelrahman S. Mayhoub and
• Sylvie Garneau-Tsodikova

Beilstein J. Org. Chem. 2013, 9, 1012–1044, doi:10.3762/bjoc.9.116

• (9) and diphenyl-1,3,4-oxadiazole (10); and thioflavin-T analogues such as benzothiazole (11), benzoxazole (12), benzofuran (13), imidazopyridine (14), and benzimidazole (15); as well as quinoline (16) and naphthalene (17) derivatives (Figure 1B). In this review, we provide an overview of these AD

• . Benzoxazoles Replacement of the sulfur of the benzothiazole backbone by oxygen affords the benzoxazole backbone. Compounds 94, 95a–n, and 96–99 (Figure 3) have also been successfully employed for radioimaging of Aβ plaques. The isosteric replacement of the sulfur of [125I]TZDM (58a) with an oxygen was designed

• target compound. SAR analysis of the compounds indicates that the benzamide moiety is favored at position 5 rather than 6 of the benzoxazole core in terms of binding affinity for Aβ plaques in vitro (Table 9). The best compound was 95e, which had a Ki value of 9.3 nM, but [123I]95e was unable to cross

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• the reactivity at the C2 position significantly. Tamagnan further reported the first example of Pd(0)/Cu(I)-catalyzed direct arylation of benzoxazole (Scheme 7) [41]. Interestingly, Bellina and Rossi reported the Pd(0)/Cu(I)-catalyzed direct arylation of indoles, imidazoles, oxazoles and thiazoles

• , which was highly effective in the direct arylation of oxazoles with various arylbromides (Scheme 7) [44]. In his initial study, Miura observed a substantial amount of C2-arylation of azoles, including benzoxazole, using Cu(I) alone as catalyst (Scheme 8) [40]. In 2007, this methodology was judiciously

• achieve Pd(0)-catalyzed direct arylation of various electron-rich heterocycles, including benzoxazole with aryl chlorides (Scheme 12) [54]. Bhanage proposed the use of 2,2,6,6-tetramethyl-3,5-heptanedione ligand (TMHD) to achieve regioselective, Pd(0)-catalyzed, direct arylation of N-methylindole

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• oxidation and an intramolecular Heck reaction [149]. Exposure of the quinone 207 to sunlight triggered the formation of benzoxazole 208, which cleaved to form an intermediate iminium salt. Subsequent proton transfer gave the vinylogous carbamate 209 (Scheme 57). After oxidation of the hydroquinone to the