Wavelength-dependent photochemistry of a diazo compound. Irradiation of 9-diazo-1,8-diazafluorene with ultraviolet or visible light

Abstract

The photochemistry of 9-diazo-l,8-diazafluorene (18DAF) depends on the wavelength of the irradiating light. When photolyzed at ca. 310 nm, into a -* absorption band, excited 18DAF rearranges to a diazirine and loses nitrogen to form the carbene 1,8-diazafluorenylidene (18FL) exclusively in the singlet state. However, when 18DAF is photolyzed at ca. 420 nm, into the -* band, no diazirine is formed, but triplet 18FL is formed directly along (4) Turro, N.

Blue light-promoted photolysis of aryldiazoacetates

“…The donor/acceptor diazo compounds 1a and 1b present an almost identical absorbance spectra in the visible region. In contrast to the acceptor-only diazo compounds 2a and 2b , both 1a and 1b display bathochromic shifts in the region of 400–500 nm (violet/blue), which can be presumably attributed to a n–π* transition of the diazo group 16 ( Fig. 1 ).…”

“…Although this photolysis phenomenon is well known for other diazocompounds using UV-light, 9 , 16 , 18 one can note here that the presence of a donor group at the aryldiazoacetates 1a and 1b (or the removal of an acceptor group, as one can observe the same trend comparing the UV-Vis absorption spectra of 2a and 2b ) is responsible for a significant bathochromic shift in their UV-Vis absorbance spectra, thus allowing the photolysis process to occur in the visible region. 10 , 16 …”

Visible Light-Promoted Amide Bond Formation via One-Pot Nitrone in Situ Formation/Rearrangement Cascade

“…Treatment of 4qa under EtOH/KOH successfully yielded Propham, a pre-and post-emergent herbicide for the control of weeds, in 83% yield (Scheme 2b). 64,65 More significantly, a straightforward, three-step, total synthesis of Amaryllidaceae alkaloid Trispheridine from 4aa was achieved in 54% overall yield (Scheme 2c). 66,67 Several control experiments were carried out to glean insight into the reaction mechanism (Scheme 3).…”

Room Temperature Coupling of Aryldiazoacetates with Boronic Acids Enhanced by Blue Light Irradiation

“…Based on these results, it is possible to observe that two competing mechanisms can be operating, depending on the reaction conditions employed, that is, photochemical and/ or thermal (dark) processes. The photochemical process is believed to involve a singlet carbene intermediate 7 , unlocked from the photolysis of aryldiazoacetate 1 . It reacts with the boronic acid partner 2 to generate the ylide 8 .…”

“…Aryldiazoacetates can absorb blue light (470–490 nm, associated to a n→π* transition) . Therefore, upon irradiation in this wavelength, aryldiazoacetates can undergo photolysis to afford singlet carbenes.…”