Photoelimination of nitrogen from adamantane and pentacycloundecane (PCU) diazirines: a spectroscopic study and supramolecular control †

Abstract

Nitrogen photoelimination delivers carbenes from diazirines. Protonation of singlet carbenes was detected based on the PCU skeleton rearrangement. Complexation of diazirines changes the relative singlet/triplet ratio of carbene products.

Ultrafast Photoelimination of Nitrogen from Upper Excited States of Diazoalkanes and the Fate of Carbenes Formed in the Reaction

“…It is generally known that singlet carbenes react with O 2 slowly ( k < 10 7 M –1 s –1 ), whereas the reaction of triplet carbenes with O 2 is much faster ( k = 10 8 –10 10 M –1 s –1 ) . Therefore, products from the irradiation of 3 in cyclohexane indicate the formation of both singlet and triplet carbene intermediates, as reported in the photochemistry of adamantane diazirine . The quantum yield for the elimination of nitrogen (Φ R ) upon excitation at 300 nm or by visible light was measured using a ferrioxalate actinometer (for details, see Table S2) in the SI. , In agreement with the photochemistry of 1 and 2 , Φ R is almost an order of magnitude larger upon excitation to a higher singlet excited state at 300 nm (Φ R = 0.34–0.36) than upon excitation to S 1 (Φ R = 0.005–0.1), indicating that 3 also undergoes anti-Kasha photochemistry.…”

Adamantane-type clusters: compounds with a ubiquitous architecture but a wide variety of compositions and unexpected materials properties

“…[565,569,569,[595][596][597] Developing efficient and selective methods for functional group transformations encompasses a wide array of chemical reactions. These reactions can include substitution, [598][599][600][601] addition, [602] and elimination reactions, [603][604][605] among others. They are applicable to various functional groups, including halides, alcohols, ketones, and carboxylic acids, among others.…”

Tricyclo[2.1.0.02,5]pent-3-ylidene: Stereoelectronic Control of Bridge-Flapping within a Nonclassical Nucleophilic Carbene

“…Singlet adamantylidene ( 1 4 ) has a C s -symmetric equilibrium geometry and undergoes degenerate bridge-flapping via C 2 v -symmetric TS­( 4 / 4 ) flap (Scheme a). ,− An analogous conformeric equilibrium has been computed for 1 (Scheme a), but its E a is considerably higher. − Another possible similarity between carbenes 1 and 4 has to do with the conduction of stereoelectronic effects through their polycyclic C-atom frameworks . An example of this is shown for prox - 4 -R, where R is an EDG (Figure ).…”

“…Dialkylcarbenes undergo rapid 1,2-H atom shift reactions if a suitable α-C–H bond is present. − This would give tricyclo­[2.1.0.0 2,5 ]­pent-2-ene ( 3 ) in the case of 1 (Scheme a) and adamantene ( 5 ) − in the case of adamantylidene ( 4 ) − (Scheme b). Carbene 4 does not yield 5 , however, because the bridgehead C–C double bond violates Bredt’s rule. − Strain within 5 , caused by the severely distorted π bond, impedes 4 → 5 .…”