10.1021/jp026641t.s001
Carlos N. Sanrame
Carlos N.
Sanrame
Christopher P. Suhrada
Christopher P.
Suhrada
Hung Dang
Hung
Dang
Miguel A. Garcia-Garibay
Miguel A.
Garcia-Garibay
Photochemistry of Crystalline Chlorodiazirines: The Influence of Conformational Disorder
and Intermolecular Cl···NN Interactions on the Solid-State Reactivity of Singlet
Chlorocarbenes<sup>†</sup>
American Chemical Society
2003
compounds 4 b
azine
carbene 5
alkene
4 c
term
solution
13 C CPMAS NMR
chlorodiazirine
formation
precursor
biphenyl
Cl
diazirine
analysis
2003-03-27 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Photochemistry_of_Crystalline_Chlorodiazirines_The_Influence_of_Conformational_Disorder_and_Intermolecular_Cl_N_N_Interactions_on_the_Solid-State_Reactivity_of_Singlet_Chlorocarbenes_sup_sup_/3724554
A photochemical study was carried out with 3-substituted 3-chlorodiazirines with 4-biphenyl- (<b>4a</b>), (4-biphenyl)methyl- (<b>4b</b>), 2-(4-biphenyl)ethyl- (<b>4c</b>), and 1,1-dimethyl-1-(4-biphenyl)methyl (<b>4d</b>) substituents. The
chlorodiazirines were prepared from the corresponding amidines (<b>7</b>) by a procedure involving oxidation with
<i>tert</i>-butyl hypochlorite under phase-transfer catalysis. The crystalline nature of <b>4a</b>−<b>d</b> was established by
differential scanning calorimetric analysis, which revealed melting endotherms prior to thermal decomposition.
Photochemical results in crystalline solids were analogous to those observed in solution, and the products
were analyzed in terms of the corresponding singlet-state chlorocarbene intermediates (<b>5a</b>−<b>d</b>). Irradiation of
<b>4a</b> in solution and in crystals resulted in formation of azine <b>9a</b> by reaction of carbene <b>5a</b> with its precursor.
Equally selective, diazirine <b>4d</b> gave alkene <b>6d</b> as the only product by a 1,2-Ph migration from carbene <b>5d</b>.
In contrast, irradiation of compounds <b>4b</b> and <b>4c</b> resulted in formation of two alkenes by 1,2-H shifts and
formation of azines by reactions of the carbenes with their precursors. The low selectivity of <b>4b</b> was rationalized
in terms of structural data from single-crystal X-ray diffraction analysis, which revealed two disordered diazirine
conformers and close Cl···N contacts between adjacent molecules. Rapid conformational equilibration in the
solid state was also suggested by solid-state <sup>13</sup>C CPMAS NMR. Similar structural effects are also postulated
to account for the solid-state reactivity of <b>4c</b>.