Matrix isolation and photochemistry of 1- and 2-naphthylchlorocarbene

Abstract

We have for the first time characterized the 1-and 2-naphthylchlorocarbenes by IR and UV/vis spectroscopy in N 2 matrices at 10 K. Although evidence suggests the presence of predominantly only one geometric isomer in the case of the 1-naphthylchlorocarbene, the IR and UV/vis spectra of the 2-naphthylchlorocarbene indicate two distinct conformations. With selective irradiation, the longer-wavelength absorbing s-Z-isomer of 2-naphthylchlorocarbene can be photochemically driven to the alternate s-E conformation. Irradiation of the 1-and 2-naphthylchlorocarbenes induces cyclization to 7-chloro-4,5-benzobicyclo[4.1.0]hepta-2,4,6-triene and 7-chloro-2,3-benzobicyclo[4.1.0]hepta-2,4,6-triene, respectively. The cyclization can be reversed by irradiation at shorter wavelengths.Our results on the singlet naphthylchlorocarbenes photochemical ring-closures parallel observations of Chapman, McMahon, and co-workers on the parent triplet 1-and 2-naphthylcarbenes (

Carbon Tunneling in the Ring Expansion of Noradamantylchlorocarbene

“…General descriptions of the low temperature apparatus and matrix isolation techniques have been published previously. 4 Diazirine 4 was co-deposited from a sample maintained at ca. -8° C, together with 100 -150 Torr N 2 (or 50 -60 Torr Ar) from a 2.5 L manifold, onto a 2.5-cm CsI window held at 21 K. Typical inert gas to diazirine ratios were estimated to be 600-800:1 for nitrogen and 400-500:1 for argon.…”

1‐Phenyl‐1,2,4,6‐cycloheptatetraene: the missing intermediate of the diphenylcarbene to fluorene rearrangement

“…Warmuth and Marvel were even able to stabilize allene 2 at room temperature inside a hemicarcerand . The equilibrium between arylcarbenes and cycloheptatetraenes was not only observed for the parent C 7 H 6 system but also for tolylcarbenes, phenylhalocarbenes, and naphthylcarbenes . Similar ring expansions were also observed in heteroarylcarbenes (e.g., in pyridylcarbenes) …”

“…[11,12] The equilibrium between arylcarbenes and cycloheptatetraenes was not only observed for the parent C 7 H 6 system but also for tolylcarbenes, [13][14][15] phenylhalocarbenes, [16] and naphthylcarbenes. [17][18][19][20][21] Similar ring expansions were also observed in heteroarylcarbenes (e.g., in pyridylcarbenes). [22] The unusual thermochemistry and photochemistry of diphenylcarbene 5 have been investigated in great detail.…”

Synthesis of a Sterically Hindered Diazirine with a Satisfactory Yield: Optically Active 2-Azicamphane

“…Moreover, the amount of decomposition varied substantially, depending on solvent composition and injector conditions that were not controllable. Yet, under the conditions employed, 2-azicamphane (5) gave a distinct GC peak accompanied by a small peak (2-3%) corresponding to the gas phase 1,3 C-H insertion product of the intermediate 2-camphanylidene (1,7,7-trimethyltricyclo[2.2.1.0 2,6 ]heptane). 7 Thus, a simple oxidative work-up (in microscale) and subsequent GC analysis was employed to monitor the course of the reaction.…”

“…The recent emergence of diazirines as popular carbene precursors can be attributed to their relative stabilities with regard to acids, bases and heat when compared with other sources. 1 That diazirines are easily photoactivated by long-wave UV light makes them not only suitable for mechanistic studies 1,2 but also as linkers for biochemical applications. 3 Consequently, efficient preparations of these compounds are in demand.…”