The Versatile Reaction Chemistry of an Alpha-Boryl Diazo Compound

Liu, Yao; Bellacasa, Raimon Puig de la; Li, Bo; Cuenca, Ana B.; Liu, Shih‐Yuan

doi:10.1021/jacs.1c06112

Cited by 16 publications

(10 citation statements)

References 70 publications

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“…Compound 7 is stable to air and moisture and can be purified via silica gel chromatography. In addition, 1,2-azaborine 3p can be converted to a BN isostere (8) of an insecticide bifenthrin 32 via a boryl diazo intermediate 33 (3p-CN2) in a four-step sequence (Fig. 4d).…”

Section: Resultsmentioning

confidence: 99%

Modular synthesis of 1,2-azaborines via ring-opening BN-isostere benzannulation

Lyu

Tugwell

Chen

et al. 2023

Preprint

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1,2-Azaborines represent a unique class of benzene isosteres that holds great potential for various applications. However, it remains a long-standing challenge to prepare monocyclic 1,2-azaborines in an efficient and modular manner. Here we report a straightforward method to directly access diverse multi-substituted 1,2-azaborines from readily available cyclopropyl imines/ketones and dibromoboranes under relatively mild conditions. The reaction is scalable, shows a broad substrate scope, and tolerates a range of functional groups. The utility of this method is demonstrated in the concise syntheses of BN isosteres of a PD-1/PD-L1 inhibitor and pyrethroid insecticide bifenthrin. Combined experimental and computational mechanistic studies suggest that the reaction pathway involves boron-mediated cyclopropane ring-opening and base-mediated elimination, followed by an unusual low-barrier 6π-electrocyclization accelerated by the BN/CC isomerism.

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Section: Resultsmentioning

confidence: 99%

Modular synthesis of 1,2-azaborines via ring-opening BN-isostere benzannulation

Lyu

Tugwell

Chen

et al. 2023

Preprint

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“…In the title compound I, the C2-C3 bond length [1.3276 (19) A ˚] resembles the bond in 1,4-cyclohexadienes [1.318 (2) A ˚] and their 1,2-azaborinine analog [1.319 (2) A ˚] more closely than that in the benzene analog (Jeffrey et al, 1988). Comparison of the title compound I with the benzene analog and three additional 1,2-azaborinine examples (Rudebusch et al, 2013;Liu et al, 2021;Pan et al, 2008) showed shorter B1-N1 [1.4052 (17)] and C2-C3 [1.3276 (19) A ˚] bond lengths. As a result of weaker bond-length compensation effects, the remaining bonds within the ring are elongated by between 0.11 and 0.15 A ˚.…”

Section: Structural Commentarymentioning

confidence: 99%

Synthesis and crystal structure of 2-(anthracen-9-yl)-1-(tert-butyldimethylsilyl)-3,6-dihydro-1λ⁴,2λ⁴-azaborinine

Gliese,

Appiarius,

Scheele

et al. 2023

Acta Cryst E

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The title compound, C24H30BNSi (I), is an asymmetric 1,2,3,6-tetrahydro-1,2-azaborinine consisting of a BN-substituted cyclohexadiene analog with a B-anthracenyl substituent. A ring-closing metathesis with subsequent substitution of the obtained BCl 1,2-azaborinine using anthracenyl lithium yielded the title compound I. The asymmetric unit (Z = 8) belongs to the orthorhombic space group Pbca and shows an elongated N—C bond compared to previously reported BN-1,4-cyclohexadiene [Abbey et al. (2008) J. Am. Chem. Soc. 130, 7250–7252]. The primarily contributing surface interactions are H...H and C...H/H...C (as elucidated by Hirshfeld surface analysis) which are dominated by van der Waals forces. Moreover, the non-aromatic BN heterocycle and the protecting group exhibit intra- and intermolecular C—H...π interactions, respectively, with the anthracenyl substituent.

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“…With the good binding affinity between nitrogen lone-pair electrons and boron's empty orbital, the amine–borane complexes have been widely applied as versatile synthetic reagents. 1 Recently, discovering interesting photo/electronic properties associated with the cyclic N–B compounds makes them an important class of heterocycles in chemical, material, and biomedical research. 2 With the discovery of BODIPY and its derivatives, the four-coordinate boron “ate” complexes have received great attention due to their interesting fluorescence (FL) properties.…”

Section: Introductionmentioning

confidence: 99%