2- Naphthylcarbene

Scheme 27 Cocyclization of the 1-naphthylcarbene complex 128 with ferf-butylphospha-alkyne 129 [91]...

With respect to the arylcarbenes, however, the carbene addition is not stereospecific the aryl-cyclopropanes are generally formed as mixtures of diastereomers. In almost all cases reported, the sj -isomer predominates, and this is the case even when the corresponding uw/z-isomer is far less sterically crowded. Thus, when 1-naphthylcarbene reacted with cyclopentene, the corresponding cyclopropane 6-(l-naphthyl)bicyclo[3.1.0]hexane (4) was obtained in 62% yield with endojexo ratio of 84 16. ... 

The dihydropyrroles are conceivably formed via a nitrile ylide, an intermediate resulting from a reaction between 1-naphthylcarbene and acetonitrile. 

Cyclizations ofcarbenes and nitrenes to form four-membered rings are extremely rare, but when no other options are available for the reactive species, such processes will occur. Thus, cyclobuta[de] naphthalene is formed in better than 40% yield from 1-naphthylcarbene in the gas phase. The same... 

These reactions are very interesting from the point of view of synthesis of novel heterocyclic compounds. Analogs are not found in the isosteric car-benes, however. 2-Diazomethylpyridine N-oxides (330) give rise to 2-acyl-pyridines (332) by photolysis or thermolysis.373,374 In view of the surprisingly facile formation of cyclobuta[de]naphthalene from 1-naphthylcarbene (see Eq. 69) the intermediate 10 jr-electron pyridooxazete 331 does not seem unreasonable (Eq. 94). Other pathways are possible too, however.273... 

LFP of 1-naphthyldiazomethane (10) in acetonitrile, the first solvent we studied, produced a transient spectrum with X = 386 nm. The transient was formed in an exponential process with a time constant of 100 10 ns and decayed over several microseconds. Our initial impulse was to attribute the transient absorbing at 386 nm to triplet 1-naphthylcarbene formed from invisible singlet 1-naphthylcarbene 11 with a time constant of 100 ns. [21]... 

Ylides of singlet 1-naphthylcarbene ( 11) with acetone, triethylamine and pyridine were soon observed. [21] Fluorenylidene was also found to react with coordinating solvents to form ylides. [22]... 

The transient spectra of neither singlet nor triplet 1-naphthylcarbene have ever been observed upon LFP of 10. The kinetics of these invisible carbenes were obtained from the growth of their ylide reaction products and not by direct observation of either singlet or triplet 1 -naphthylcarbene. 

The study of the 1-naphthylcarbene system is an example of the use of probe kinetics, first employed in great detail by Scaiano and coworkers in the study of radicals and biradicals. [23]... 

The situation with 1-naphthylcarbene is by no means unique. The invisibility of singlet and triplet non-aromatic carbenes makes studying their kinetics even more challenging. In fact, in our opinion the most interesting carbenes lack useful chromophores for laser flash photolysis studies. 

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