Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

• Hisham Qrareya,
• Lorenzo Meazza,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 3008–3014, doi:10.3762/bjoc.16.250

• . Keywords: aryl phosphates; biarenes; metal-free synthesis; photochemistry; photoextrusion; Introduction It is difficult to overestimate the importance of aromatics in drug development. Indeed, introducing an aromatic or a heteroaromatic ring, most often a (substituted) phenyl ring, into a biologically

• intermediates (triplet aryl cations [28][29] or aryl radicals [30][31]). As for the former case, the intermolecular formation of a biaryl arose from the photoheterolysis of an Ar–N bond (in arene diazonium salts or their derivatives [32][33]), of an Ar–Cl bond [34][35], of an Ar–O bond (in aryl phosphates [36

• that the fluorescence is significantly red shifted (about 30 nm) with respect to that of the corresponding diethyl aryl phosphates (see Figure 1 and Figure 2). On the other hand, when focusing on compound 3a, we noticed the presence of two emission bands located at 307 and 360 nm, respectively (see

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

• is very negative, −1.28, suggesting that the cleavage of the P–O5´ bond is rather advanced in the transition state. However, the βlg value obtained with uridine 3´-aryl phosphates is much less negative, −0.54 [51]. When the data of alkyl and aryl esters is included in the same free energy plot, a

• state resembles the transition of ribonucleoside 3´-aryl phosphates rather than 3´-alkyl phosphates, which is expected on the basis of 105-fold lower basicity of sulfide ions compared to alkoxide ions. The effect of non-bridging thiosubstitution on the cleavage rate is modest compared to the bridging

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

• , Scheme 11) compared with the alkoxylation of structures 46–49 [64]. Under similar conditions, aryl phosphates and benzyl phosphonic monoacids were subjected to ortho-acetoxylation in the presence of the Pd(OAc)2/PhI(OAc)2 system; (diacetoxyiodo)benzene served as the source of the acetoxy group [65]. The

Photorelease of phosphates: Mild methods for protecting phosphate derivatives

• Sanjeewa N. Senadheera,
• Abraham L. Yousef and
• Richard S. Givens

Beilstein J. Org. Chem. 2014, 10, 2038–2054, doi:10.3762/bjoc.10.212

• rearrangement; photoremovable protecting groups; Introduction Phosphates have long held an important formative position in the development of organic photochemistry beginning with the seminal report by Havinga [1] of the unusual substituent effects in the photosolvolysis of aryl phosphates that showed

• unexpectedly pronounced meta activation of substituted aryl phosphates. A strong ‘meta effect’ resulting in enhanced reaction efficiency by electron withdrawing, meta substituents is contrary to their ground state effects on solvolysis reactions which, instead, display enhanced reactivity for para substituents

Atherton–Todd reaction: mechanism, scope and applications

• Stéphanie S. Le Corre,
• Mathieu Berchel,
• Hélène Couthon-Gourvès,
• Jean-Pierre Haelters and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2014, 10, 1166–1196, doi:10.3762/bjoc.10.117

• a halide source. Even though the yield is usually lower compared to classical AT conditions, this result opens new perspectives for the development of green processes. 4. Applications 4.1 Synthetic utilities of AT reactions In this section we will discuss the use of AT reactions to produce aryl

• phosphates or phosphoramidates which are important intermediates for a variety of subsequent transformations or can be used as organocatalysts. Aryl dialkyl phosphates, prepared by the AT reaction from phenol derivatives, were employed to reduce phenol functional groups. It is noteworthy that phenol