24(1).PDF24(2).PDF24(3).PDF24(4).PDF24(5).PDF24(6).PDF24(7).PDF24(8).PDF24(9).PDF24(10).PDF) v-{Reprioted froo the Journal ol the Aoericen Cbeoiccl Society,91,20Og (1g0g).1Copyrigbt 1969 by tbe Aoericra Cbcrnicel Socicty ead reprioted by pernissioo of tbe copyright orocr.Irradiation of cis ,cis-l ,S.Cyclooctadiene inthe Presence of copper(I) chlorideGeorge M. Whitesides, Gerald L. Goe, and Arthur C. CopeIrradiation of cls ,cis-l,5-Cyclooctadiene in the Presence ofCopper(I) Chloride'George NI. \l'hitesides, Gerald L. Goe,:" and Arthur C. Cope2bContributiott J'rorn the Departntent oJ'Cltenti.strt', ilIassac'husetts Itrstirure of'Technologl', Canrhridge, Llassacltusetts 02139. Receivetl Septembar t0. 1968Abstract: Irradiation of an oxygen-frce pent:.tne suspcnsion of di-tt-chloro-bis(crs.crs- 1,5-cycloocradiene)dicopper-(l) (4) at 254-ms yields, in addition to tricyclo[].1.0.0:'t,loctlnc (t). sigrrificilnr quantitics of insoluble copper(l)comple.res of cis,tratrs- and tratts,trons-1.5-cyclooctldienes. Exumination of the photocfternical behavior of thesedienes, and of their yields relative to the yield of I during thc irradiation ol {. indicates that a rlajor part of the Iformed hlts cls,trarrs-1,5-cyclooctadiene as x prccursor. These data furrher suggest that a significant part of thephotoconversion of cis,tratrs-1,5-cyclooctadicne to I may take placc lrcr the intermedilrcy' of tratts,trytrrs-1,5-cyclooctadiene./r---.'r--x// |/-Jx--'2a2b-rrI ransition metals catalyze the thermal and photo-I chemical dimerization of a wide variety of olefins.3-8One of the most interesting of the metal-catalyzed photo-chemical reactions is the conversion of crs,cls- 1,S-cyclo-octadiene to tricyclo[3.3.0.02'6]octane (l) by irradiationin the presence of copper(l) chloride, or by photosensiti-zation with mercury (3P,) atoms.s'a Although the basicmechanism of the gas-phase, mercury-photosensitizedreaction has been established,a neither the mechanism(s)of the condensed-phase, copper-catalyzed photochemicalreaction nor the nature of any intermediates in thisreaction have yet been clearly defined.The copper ion in the latter reaction might a priori(l) Supported in part by the U. S. Army Research Office (Durham),Grant ARO(D)-31-12.1-.135, and by the National Science Foundation,Crants GP-6222 and CP-7266.(2) (a) National Science Foundation Predoctoral Fellow, 196l-1966:National Institutes of Health Predoctoral Fellow, 1966-1967. (b)Deceased June 4, 1966.(3) R. Srinivasan, J. Arner. Chem. Soc., 86, 33lS (1964).(4) I. Haller and R. Srinivasan, ibid.,88,5084 (1966).(5) F. D. Mango and J. H. Schachtschneider, ibid., 89, 2485 (1967).(6) J. J. ivlrowca and T. J. Katz, ibid.,88,4012 (1966), and referencestherein.(7) W. Merk and R. Pettir, ibid.,89,4787,11-BB (1967).(8) D.J. Trecker, R. S. Foote, J. P. Henry, and J. E. McKeon, ibid.,88, 302r 0966).serve a variety of functions: r'i:., as a photosensitizer, asa "template" controlling the stereochemistry of reactionof coordinated excited olefinic ligands, or as a catalysrfacilitating carbon-carbon bond formation through mix-ing of appropriate metal orbitals with olefinic molecularorbitals.t On the basis of quantum yield measurements.Srinivasan has su_egested that the primary photochemicalstep under the homogeneous reaction conditions of hisexperiments involves absorption of light by uncomplexedcis,cis-I,5-cyclooctadiene. He further proposed that thccopper(l) atom exerted its influence in the reaction in thesubsequent stabilization of the initially tormed excitedstate of the olefin by formation of a complex of un-specified structure (represented schematically by 3).lHowever, the appealing geometrical relation between Iand the racemic conformation of trans,trans-1,5-cyclo-octadiene (2a), and the complicated and quite differentmechanism suggested for the superficially similar copper-catalyzed photochemical dimerization of norbornene.sJournal of the American Chemical Society I 9l:10 I Ntay 7, 1969/.\ol* "CuCl" ->26()9actually consists of a mixture of several species. 3fltlprobably contains appreciable quantities of both com-plexed and uncomplexed crs,crs- 1,5-cyclooctadiene ; horr'-ever, accurate estimates of the relative quantities ofcomplexed and uncomplexed diene cannot be obtainedfrom the available data.In a typical experiment, a stirred, degassed pentancsuspension of complex .l was irradiated for ca.24 hr atroom temperature using low-pressure mercury lanrps,and the solid material present at the end of the reacrionwas separated by filtration. The filtered solution wasshown by glpc to contain cls,crs-1,5-cyclooc'adiene tndtricyclooctane I as major components, and cls,crs- l.-1-cyclooctadiene, .l-vinylcyclohexene, and three unidenti-fied components as minor constituents.t2 The solidmaterial was composed of a mixture of copper(l) chloridcand copper(l) olefin complexes. Trearment of this mix-ture with aqueous sodium cyanide solution liberated theolefinic components. E.xtraction and glpc analysis ot'the freed olefins indicated the presence of both crs.cis-and cis,trans-I.5-cyclooctadiene,t3 as well as a smallquantity of another component, to which we have assignedthe trans.trans-I,5-cyclooctadiene structure 2 on the basisof the chemical and spectrcscopic evidence which follow's.Compound 2 could be isolated in pure form by glpcunder ctrefully controlled conditions. This compt>undproved to be very sensitive to traces of oxygen or aciti.and slorvly polymerized thermally even in the absencc t)i'thcse agcnts. It was indc-finirely stable while tiozen rr- 78" under an inert atmosphere, and reasonably stablcin dilute solution in degassed aprotic solvents. It polv-merized explosively on the addition of solvent that hatinot been deoxvgenated. It was characterized by unodor similar to those of cis,trarrs-1,5-cyclooctadiene andtrans-cyclooctene.The infrared spectrum of 2 showed bands at l6t5(C-C stretching vibration) and 985 cm - L (trans-olelinbending vibrarion). No bands appeared in the 650-750-cm-t region.ra The observed double-bond stretch-ing frequency is lower than that of cis,trans-1,5-cvclo-octadiene (1630 cnt -t in the ir spectrum; peaks of equalintensity at 1622 and 1635 cm-t in the Raman spec-trumr3;, which in turn is lorver than that of crs,crs-1,5-cyclooctadiene (1655 cm-r in the ir spectrum, and l66Jcm-r in the Raman spectrumrr).The mass spectra of the I,3-, 1,4-, and 1,5-cyclo-octadienes are strikingly similar in the regions corresoond-ing to fra*qments