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The influence of skeletal geometry on the n → π cd of bridged-ring lactones and lactams
Tetrahedron Letters No.55, pp.4897-4898, 1969.
IiEINFLUENCEOFSKELEWLGEOMElWONlIEn
Pergamon Press.
Printed in Great Britain.
+n*CDOFBRIEEWRI~bAC!ItlNESAND~
A. F. Beecham Divisicmof olemicalPhysics,CSIRO ChemicalResearch Laboratories,P.O. Box 160, Claytan,Victoria,Australia 3168.
Received in the UK
17 October;acceptedfor publication29 October 1969
A relationship,in lactcnes,between the sigh of the n + n* Cotton effect and the chiral sense of the la&one ring itself has been suggestedrecently (l-4). Four publications list the ORD (5-7) or CD (8) of thirty-nineccmpoucdsinwhich the lactcmegroup bridges a sixca&on ring. Ammg these, throughring-fusionandthrough single substituents,thexeare different patterns
fifteen
of directsubstituticmcm thebridged-x+ng,butthe relationshipindicatedby I
and II is found to hold without exception. On present evidence, therefore,the sign of the CH.
I
-W?
II
+ve
CH,
III --ve
IV
We
n + TI*Cotta effect dependssolely rm the enantiamsricnatute of the bridged-ringsystem and not at all cm molecularasymaetxyperipheralto this. Ring geanetrymybe
equallyimportantin lactams (1). In the iscmsriccamphorolactam,
III and IV, Basch et. al. (9) remarkedthat the quadmnt rule for the sigh of the amide n + II* CD (10) would predict a positive Cotton effect for III. A negativecne is, in fact, observed,as
#OH
&OH V
CH<
&!-OO VI
CHi
VII
in lactonesof type I. Gc&rsn et. al. (11) found that, &-I each of three differentsolvents,the CD curves fmn III and IV were mirror images. Since the geanstricrelaticmshipsbetween the bridgeheadmethylgroup and the lactmchrmophore
are quite different
in
the two canpounds, it
is evident that the enantianericbridged-ringskeletonsdeterminethe sign of the CD.
4897
4890
No.55
'Ihemirrorimage relaticmshipsof the CDcuxves suggestthatthe degree of dissymmetry in then +n* tMnsitionis also determinedby the ring-gecmetcy. 'Ihesame conclusianwas reached with respect to y-la&ones ofaldcmic acids (3) on the grounds of observedccnstancyin the dissymnetxyfactor (12). As shown in the Table, this factor, IFI,
is alsoccmstantinquinide,
V, acetonequinide,VI, andtetrahytipyrenylactanzquinide, VII, three bridged-ringlactonesof SkeletaltypeI.
lhe ORD amplitudesof V and VI differ (7) by over 50%. In Water
Md
c_ V
114 216mp
VI
89 216mu
In Methanol I"1
%U -2'g4217m -2'22217mu
0.026
*LX
105220m!_l -2'g3220mu
0.025
insOlUble
VII
&)(
g*219mLl 11222lmu
The transiticnp&xbility,measuredby
I”1 0.028
-2.4622Om)l 0.025 -2.76223mu
0.025
E, variesbetweenthetireeccxnpounds
andalso varies in the same ccmpoundwith change in solvent. However, the CD varies correspcndingly, so that IFI remains ccmstant. A ccmstantsourceof dissynmetryin the -sition
is inplied; canixm to all three moleculesand unaffectedby the differencesin
substitutionor solvation. This *
cmly be allorpart of the cumnon skeletal structure.
REFERENCES 1.
H. Wolf, TetrahedronLetters, 1075 (1965).
2.
M. Legrand and R. Buzourt,Bull. See. Chim. E'rance, 2241 (1967).
3.
A. F. Beecham,TetrehedronLetters,2355 (1968).
4.
A. F. Beecham,TetrahedronLetters, 3591 (1968).
5.
J. P. Jennings,W. Klyne and P. M. Scopes, J. Chem. Sot., 7229 (1965).
6.
C. G. IkGrezia,W. Klyne, P. M. Scopes, D. R. Sparrow and W. B. Whalley, J. Chem. See. (C) 896 (1966).
7.
W. G&field, A. C. Weiss jun. and J. Gorse, J. Chem. See. (Cl, 1885 (1966).
8.
H. Meguro, K. Tuzimuraand N. Takahashi,Tettiedron Letters, 6305 (1968).
9.
H. Basch, M. B. Robin and N. A. Kuebler,J. Chem. Phys., g, 5007 (1968).
10.
B. J. Libran and J. A. Schellman,J. Phys. Chem., =69,
11.
M. Godnan,
12.
W. Kuhn, Ann. Rev. Phys. Chem., 2, 417 (1958).
978
(1965).
C. Toni.010 and J. Falietta,J. Amer. Chem. Sot., 2,
3816 (1969).
IiEINFLUENCEOFSKELEWLGEOMElWONlIEn
Pergamon Press.
Printed in Great Britain.
+n*CDOFBRIEEWRI~bAC!ItlNESAND~
A. F. Beecham Divisicmof olemicalPhysics,CSIRO ChemicalResearch Laboratories,P.O. Box 160, Claytan,Victoria,Australia 3168.
Received in the UK
17 October;acceptedfor publication29 October 1969
A relationship,in lactcnes,between the sigh of the n + n* Cotton effect and the chiral sense of the la&one ring itself has been suggestedrecently (l-4). Four publications list the ORD (5-7) or CD (8) of thirty-nineccmpoucdsinwhich the lactcmegroup bridges a sixca&on ring. Ammg these, throughring-fusionandthrough single substituents,thexeare different patterns
fifteen
of directsubstituticmcm thebridged-x+ng,butthe relationshipindicatedby I
and II is found to hold without exception. On present evidence, therefore,the sign of the CH.
I
-W?
II
+ve
CH,
III --ve
IV
We
n + TI*Cotta effect dependssolely rm the enantiamsricnatute of the bridged-ringsystem and not at all cm molecularasymaetxyperipheralto this. Ring geanetrymybe
equallyimportantin lactams (1). In the iscmsriccamphorolactam,
III and IV, Basch et. al. (9) remarkedthat the quadmnt rule for the sigh of the amide n + II* CD (10) would predict a positive Cotton effect for III. A negativecne is, in fact, observed,as
#OH
&OH V
CH<
&!-OO VI
CHi
VII
in lactonesof type I. Gc&rsn et. al. (11) found that, &-I each of three differentsolvents,the CD curves fmn III and IV were mirror images. Since the geanstricrelaticmshipsbetween the bridgeheadmethylgroup and the lactmchrmophore
are quite different
in
the two canpounds, it
is evident that the enantianericbridged-ringskeletonsdeterminethe sign of the CD.
4897
4890
No.55
'Ihemirrorimage relaticmshipsof the CDcuxves suggestthatthe degree of dissymmetry in then +n* tMnsitionis also determinedby the ring-gecmetcy. 'Ihesame conclusianwas reached with respect to y-la&ones ofaldcmic acids (3) on the grounds of observedccnstancyin the dissymnetxyfactor (12). As shown in the Table, this factor, IFI,
is alsoccmstantinquinide,
V, acetonequinide,VI, andtetrahytipyrenylactanzquinide, VII, three bridged-ringlactonesof SkeletaltypeI.
lhe ORD amplitudesof V and VI differ (7) by over 50%. In Water
Md
c_ V
114 216mp
VI
89 216mu
In Methanol I"1
%U -2'g4217m -2'22217mu
0.026
*LX
105220m!_l -2'g3220mu
0.025
insOlUble
VII
&)(
g*219mLl 11222lmu
The transiticnp&xbility,measuredby
I”1 0.028
-2.4622Om)l 0.025 -2.76223mu
0.025
E, variesbetweenthetireeccxnpounds
andalso varies in the same ccmpoundwith change in solvent. However, the CD varies correspcndingly, so that IFI remains ccmstant. A ccmstantsourceof dissynmetryin the -sition
is inplied; canixm to all three moleculesand unaffectedby the differencesin
substitutionor solvation. This *
cmly be allorpart of the cumnon skeletal structure.
REFERENCES 1.
H. Wolf, TetrahedronLetters, 1075 (1965).
2.
M. Legrand and R. Buzourt,Bull. See. Chim. E'rance, 2241 (1967).
3.
A. F. Beecham,TetrehedronLetters,2355 (1968).
4.
A. F. Beecham,TetrahedronLetters, 3591 (1968).
5.
J. P. Jennings,W. Klyne and P. M. Scopes, J. Chem. Sot., 7229 (1965).
6.
C. G. IkGrezia,W. Klyne, P. M. Scopes, D. R. Sparrow and W. B. Whalley, J. Chem. See. (C) 896 (1966).
7.
W. G&field, A. C. Weiss jun. and J. Gorse, J. Chem. See. (Cl, 1885 (1966).
8.
H. Meguro, K. Tuzimuraand N. Takahashi,Tettiedron Letters, 6305 (1968).
9.
H. Basch, M. B. Robin and N. A. Kuebler,J. Chem. Phys., g, 5007 (1968).
10.
B. J. Libran and J. A. Schellman,J. Phys. Chem., =69,
11.
M. Godnan,
12.
W. Kuhn, Ann. Rev. Phys. Chem., 2, 417 (1958).
978
(1965).
C. Toni.010 and J. Falietta,J. Amer. Chem. Sot., 2,
3816 (1969).