Face Selectivity in the Diels‐Alder Additions and Chelotropic Addition of Sulfur Dioxide to 2‐(D)Methylidene‐3‐methylidenebicyclo[2.2.1]heptane

Abstract

The stereoselectivity of the cycloadditions of 2-(D)methylidene-3-methylidenebicyclo[2.2. llheptane (4) to various dienophiles has been determined. The exo-us. endo-face selectivity depends on the type of dienophiles, and for olefinic ones, on the mode of attack (Alder-us. anti-Alder endo rule). It is > 9:1 with N-phenyltriazolinedione (NPTAD) and ethylenetetracarbonitrile (TCNE), < 1 :9 with dimethyl acetylenedicarboxylate (DMAD), 30 f 5:70 i 5 with DMAD in the presence of AICl,, 15 f 5:85 f 5 with dehydrobenzene and 40 f S:60 f 5 with ' 0 2 generated photochemically ( Table I ) . With para-benzoquinone and maleic anhydride, the exo-us. endo-face selectivity is < 1.9 and 20 f 5:80 f 5, respectively, for their anti-Alder mode of attack; it is 50 i 5:50 f. 5 and 55 f 5 :45 * 5, respectively, for their Alder mode of reaction. Under conditions of kinetic control, the chelotropic addition of SO, to 4 is endo-face selective.Face selectivity can be observed for reactions of a n-function attached to a skeleton which is not symmetrical with respect to the 'n-plane' of this function [l] [2]. The face selectivity of the Diels-Alder additions of isodicyclopentadiene ( = 4,5,6,7-tetrahydro-4,7-methano-2H-indene; 1 was first studied by Alder and coworkers . A large variety of dienophiles were found to add to 1 preferentially onto its endo face. This was attributed by Paquette and Gleiter [5] to a kinetic stereoelectronic factor. According to these authors, the norbornane skeleton causes mixing of and II orbitals of the diene moiety such that the symmetrical subHOMO (n,) of the diene of 1 tilts its terminal p orbitals inward in the exo face of the norbornane moiety, and outward in the endo face. When a dienophile approaching from the endo face closed-shell repulsion between the dienophile HOMO and the tilted n, orbital of the diene is avoided. These two orbitals would overlap more in a exo -face attack.Bartlett et al. [7] reported, however, that the face selectivity for the cycloadditions of maleic anhydride to 1 can be reversed by changing the solvent. Later, Paquette et a/. [6] found that the Diels-Alder addition of N-methyltriazolinedione (NMTAD) and Nphenyltriazolinedione (NPTAD) to 1 were highly exo -face selective whereas those to the didehydro analog 2 were endo -face selective.

Face selectivity of the Diels‐Alder additions and cheletropic additions of sulfur dioxide to 2‐ vinyl‐7‐oxabicyclo[2.2.1]hept‐2‐ene derivatives

“…The face selectivity depends on the nature of the bridges that constitute the bicyclic system, on the nature of the dienophile, and in some cases on the solvent [ 131. The results were interpreted in terms of stereoelectronic factors [ le,f,g,h], of torsional effects [4] [14], and of steric hindrance [8] [ll] [15]. In the case of semicyclic 1,3-dienes grafted onto monocyclic skeletons (e.g.…”

“…): 322 (0.5, M f ' ) , 307 (0.8), 293(23), 263(8), 235(2), 219(lo), 189 (12), 86 (73), 73 (100). Anal.…”

ChemInform Abstract: Control of Diels‐Alder Addition, Stereo‐ and Regioselectivity by Remote Substituents and Tricarbonyl(diene)iron Moieties.

“…This type of interaction had been proposed earlier to explain the 'meta' regioselectivity of the cycloaddition of 15 to 5,6-dimethylidenebicyclo[2.2.l]heptan-2-endo-o1(62) [20]. In the latter reaction, one implies the endo face of the diene moiety to be favored for the dienophile attack, a property which has been demonstrated for deuterium-substituted s-cis-butadienes grafted onto bicyclo[2.2.1]heptane skeletons [21]. In contrast, and as for the cycloadditions 12 + 15, 13 + 15, 13 + 16, and 13 + CVA, the Diels-Alder additions of 15 to the acetate 63 and brosylate 64…”

“…Mixture of Tricarbonyl((1 RS,R RS.YRS,IOSR,l I RS)-C.9,IO,C-q-(methyl Il-hydroxy-9,10-dimethylidenetricyclo[6.2.2.O2~7]dodeca-2.4,6-triene-4-carboxylute)]iron (21) and Tricurbonyl[(lRS,61 RS,9SR,IORS,IZRS)- C,9,10, C-q-(methyl I2-hydroxy-9.IO-dimethylidenetri~yclo[4.2.2.0~~~]dodeca-2,4,6-triene-4-carboxylatej]iron (20). A mixture of 18/19/20/2l (see above; 30 mg), anh.…”

Tandem Diels‐Alder Reactivity Controlled by Remote Substituents. Regioselective synthesis of linearly annellated six‐membered ring systems from (1RS,5SR,6RS,7SR)‐6,7‐bis(chloromethyl)‐8,9‐dimethylidene‐2‐oxabicyclo[3.2.2]nonan‐3‐one. Crystal structure of (1RS,5RS,6SR,11RS)‐6,7‐bis(chloromethyl)‐3‐oxo‐2‐oxatricyclo[7.4.0.1,5]tridec‐8‐en‐11‐yl methyl ketone

“…TLC on silica gel (CH2C12/acetone 95 :5) yielding 31 mg (23'1/0), amorphous solid. 'H-NMR (360 MHz, CD2CI,): 7.12 (m, H-C(I0)); 6.89 (.Y, H-C(6)); 3.75 (s, MeO, CH,(c()); 3.57 (m. CHz (5) d,'J(C,H)=162,C(6));133.8,133.1,130.3,130.0,129.6(5s,arom.C);128.0(d,1J(C,H)=154,C(10));127.6(s, C(7)); 51.2 (12), 71 (lo), 59 (33). Methyl 3-Acetyl-I,2,3,4,5,8-hexnhydr~~-7-(m~thoxycnrbonyl)anthrncene-Y-yl Acetnte (45).…”