Controlled oligomerization of [1.1.1]propellane through radical polarity matching: selective synthesis of SF₅- and CF₃SF₄-containing [2]staffanes

• Jón Atiba Buldt,
• Wang-Yeuk Kong,
• Yannick Kraemer,
• Masiel M. Belsuzarri,
• Ansh Hiten Patel,
• James C. Fettinger,
• Dean J. Tantillo and
• Cody Ross Pitts

Beilstein J. Org. Chem. 2024, 20, 3134–3143, doi:10.3762/bjoc.20.259

• -containing [2]staffane in the solid state. Keywords: pentafluorosulfanylation; [1.1.1]propellane; radical chain oligomerization; staffanes; strain-release; Introduction In various radical additions of X–Y across [1.1.1]propellane (1), functionalized oligomers known as [n]staffanes – with n > 1, where n

• synthetic challenge. Herein, we report proof-of-concept that our previous work on strain-release pentafluorosulfanylation of 1 [36] using SF5Cl (prepared in house [37] under mild oxidative fluorination conditions [38][39][40][41][42][43][44]) can be extended to the selective synthesis of the associated

• cooling; this highlights that the [2]staffanes synthesized during this study are also interesting from a fundamental structural standpoint. Results and Discussion Over the past few years, our group has begun to establish strain-release pentafluorosulfanylation as a viable strategy for C(sp3)–SF5 bond

Advances in radical peroxidation with hydroperoxides

• Oleg V. Bityukov,
• Pavel Yu. Serdyuchenko,
• Andrey S. Kirillov,
• Gennady I. Nikishin,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249

• subsequent β C–C scission of radical B produces the β-keto radical E, driven by strain release. Further alkene 127 adds the β-keto radical E to form the C-centered radical F. The Fe(III)OO-t-Bu complex D resulted from the Fe(II)/Fe(III) catalytic cycle reacts with radical F to yield the target product 129. A

Ring opening of photogenerated azetidinols as a strategy for the synthesis of aminodioxolanes

• Henning Maag,
• Daniel J. Lemcke and
• Johannes M. Wahl

Beilstein J. Org. Chem. 2024, 20, 1671–1676, doi:10.3762/bjoc.20.148

• , endergonic transformations can be realized [3]. A promising strategy for the synthesis of complex products lies in the combination of photochemical cyclization and strain-release reaction (Scheme 1a) [4]. In this ‘build and release approach’, a simple precursor is cyclized upon irradiation. Subsequently, a

(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• itself accessible in good yields from allyl chloride 1 using a route based on that reported by Schlüter [28]. Bifunctional 1,2-BCP (±)-4 bearing orthogonally protected alcohol functionalities was obtained from 3a through a three-step sequence of strain-release radical ring-opening with iodochloromethane

• . Bennet and co-workers also reported the synthesis of 1-amino-1,2-BCPs (±)-11a–e via a similar strategy (Scheme 1C) [29]. They were able to prepare differently-substituted [1.1.1]propellanes 3b–f and subject these to strain-release amination reactions. The synthesis was shown to tolerate typical alcohol

• 1,5-BCHeps is slightly smaller than in meta-benzene but the substituent and dihedral angles are remarkably similar. 1,5-BCHeps 126 and 127 were first reported by Gassman and Proehl [61] and by Wada [62]. The most common synthetic approach today is via the strain-release ring-opening of [3.1.1

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

• bridging heteroatom increases the ring-strain energy of the system, conceptualized by the decrease in bond distances. Typically, there are two modes for ring-strain release. First, functionalization of the double bond mildly alleviates the ring strain by relieving nonoptimal bond angles enforced by the

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• 104–107 range [39][40][41][43][48][68]. Thus, while introducing one CF3 group dramatically alters the reactivity, an additional CF3 group does not seem to significantly impact the reactivity any further. The hypothesis of a ground-state strain release to explain this behavior was discarded as an

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• was a strain release upon opening the dimeric species 60. The multiple rearrangements as discussed so far are complex and fascinating but in most of the cases they represent irreversible transformations which prevent a use in reversible switching processes. A multistate reversible transformation

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• carboxylates. Aminyl and aminium radical generation The prevalent strategy for accessing aminium radicals is SET oxidations. The efficiency of this approach is closely related to the stabilization of the generated radical on the substrate (delocalization, electronic effects) or through a strain release ring

• excited state, together with an intense absorption in the visible-light region. The transformation proceeds via the single-electron oxidation of 2H-azirines, forming a nitrogen-centered radical cation, which is prone to ring opening. The driving force of the ring strain release and irreversible ring

• . In 2011, König and co-workers [150] demonstrated that eosin Y (OD13) was an efficient dye for an aza-Henry reaction [151], affording the tetrahydroquinolines 34.2 (Scheme 34). Simultaneously, the Tan group described the use of rose bengal (OD15) in the same transformation [152]. Regarding the strain