Vibrational spectra are reported for cubane, cubane-t/i, .rym-cubane-ti/2, Ym-cubane-í/6, and cubane-t/g-Infrared spectra are from 400 to 3600 cm-1 for CS2 and CCI4 solutions, and for a solid deposited from the vapor at ~100 K. Raman spectra are for the same solutions and for the polycrystalline solid at room temperature. Vibrational assignments have been made for all the fundamentals of all five compounds, 120 modes in all. The fortuitous crystal structure of cubane and cubane-/g was an important aid. Of the 18 fundamentals of cubane, only one or two are not certain. The spectra show almost no effect of the severe bond angle strain. Also there are no low molecular modes; the lowest for cubane is 617 cm'1.

The syntheses of deuterocubane, 1,4-dideuterocubane, 1,2,3,4,6,7- hexadeuterocubane, and octa-deuterocubane of high isotopic purity are described. Several new derivatives of cubane were characterized, and an improved procedure for the decarboxylation of carboxylic acids via their t-butyl peroxy esters is suggested.

The regiochemistry of the Diels-Alder reaction between cyclopentadienone and 6,6-dimethylfulvene (isopropylidenecyclopentadiene) has been studied. Two adducts (in addition to cyclopentadienone dimer) were isolated and their structures were shown to be endo-10-isopropylidenetricyclo[5,2,1,02,6]-deca-4,8- dien-3-one (6a) and endo-3-isopropylidenetricyclo[5,2,1,02,6]deca-4,8- dien-10-one (7a). Kinetic parameters for the Cope rearrangement (6a) ↔ (7a) have been determined. The adducts (6a) and (7a) were formed in the ratio 45 : 55 respectively. Thus, in contrast to FMO predictions, and to its reaction with cyclopentadiene, cyclopentadienone tends to behave as a diene towards the fulvene. A tentative explanation of these results, based on angle strain in the transition states for the formation of Diels-Alder adducts, is proposed.

Relative rate constants for the Birch reduction (Li/liq. NH3/ButOH) of the three isomeric hexahydrodimethanonaphthalenes (3)-(5) and the octahydro analogues (10)-(13) were obtained and compared with those obtained for the reduction of norbornadiene and norbornene from an earlier study. Diene (5) was reduced almost 2000 times more rapidly than norbornene and 20000 times more rapidly than the monoene (13). Rate-enhancement factors for dienes (3) and (4) were less substantial but meaningful: 19 for (3) [compared with (10)] and 35 for (4) [compared with (12)]. These rate enhancements were attributed to the operation of π* orbital interactions through space in diene (5) and to the presence of π* orbital interactions through four bonds in dienes (3) and (4). The existence of a linear relationship between the natural logarithm of the rate of reduction of a substrate and its LUMO energy (obtained from either gas-phase electron affinities or ab initio MO calculations) supports this conclusion. The only-fair correlation of the above relationship was attributed to the neglect of other factors, such as the electronic structure and the geometry of the anion radical, which contribute to the overall rate of the Birch reduction. These two factors were explored by using PMO theory and ab initio MO calculations. In particular, full geometry optimizations (UHF, STO-3G basis set) on the anion radicals of norbornadiene (1) (C2v symmetry constraint) and norbornene (22) (Cs symmetry constraint) were carried out, and their geometries reported. Noteworthy is the strong pyramidalization of the olehic centres of (1) and (22) in the endo direction. These pyramidalizations explain the observed stereoselective exo protonation of the anion radical of (1), and also the much faster rate of reduction of (1) compared with (5), since the pyramidalization in the anion radical of (5) is such as to hinder protonation. The geometries of anion radicals appear to have a profound effect on rates, on stereoselectivity of protonation, and on the structures of the final products, and this is discussed in detail. The synthesis of the diene (3) is also described.

The synthesis of (adamantan-1-y1)trimethylstannane (I), (bicyclo[2,2,2]oct-1-y1)trimethylstannane (2), (bicyclo[2,2,l]hept-1-yl)trimethylstannane (3), (cubanyl)trimethylstannane(4) and(tricycl0[4,1,1,0~,~]hept-1-y1)trimethylstannane (5) is described and the carbon-13 nuclear magnetic resonance spectra of these compounds are reported. In particular, it is found that the coupling constant of the directly bonded tin bridgehead carbon atoms is not greatly dependent on the degree of s character of the carbon exocyclic bonding orbital and that vicinal coupling between tin and carbon is observed to fit a Karplus equation. A linear relationship occurs between 1J("7,"9Sn,'3CM,) and 2J(117'119Sn,1HM,).