Face Selectivity of the Diels‐Alder Additions of Exocyclic Dienes Grafted onto 7‐Oxabicyclo[2.2.1]heptanes

Abstract

(18), respectively, without loss of the olefin configuration. Ethylene tetracarbonitrile (TCE) and N-phenyltriazolinedione (NPTAD) added to these new exocyclic dienes and tetraenes preferentially onto their exo-face. The same face selectivity was observed for the cycloadditions of TCE to the (Z)-and (E)-chlorodienes 9 and 10, thus realizing a case where the kinetic stereoselectivity of the additions is proven not to be governed by the stability of the adducts. The exo-face selectivity of the Diels-Alder additions of dienes grafted onto 7-oxabicyclo [2.2. llheptanes contrasts with the endo-face selectivity reported for a large number of cycloadditions of dienes grafted onto bicyclo [2.2. llheptane skeletons.

1H‐NMR Spectra of Cyclohexa‐1,4‐dienes and Cyclohexenes Annellated to Bicyclo[2.2.1]hept‐2‐enes. The Inter‐Ring Homoallylic H,H Coupling Constants as Stereochemical Probes

“…Half chairs are expected for the cyclohexene-tetracarbonitriles 22-32 with the substituent at C(3) in a pseudoequatorial position. This was confirmed by the analysis of the intra-ring 'J(H,H) [5] [25] and by comparison with the observed and simulated 'H-NMR spectra of 3-chloro-cyclohex-4-ene-1,1,2,2-tetracarbonitrile (see Table 2, Fig. 2).…”

“…This suggests that the a-framework contributes significantly in differentiating the longrange coupling constants reported here. As for 7-1 2, the d,, of Hexo -C(3) and Hexo -C(6) was slightly larger than that of the corresponding Hendo's (Ad, = 0.14 ppm in 22 and 24, 0.37 ppm in 23, 0.29 pprn in 25, and 0.44 ppm in 30 [5] for the 2 H-C(6); see Table I ) . Half chairs are expected for the cyclohexene-tetracarbonitriles 22-32 with the substituent at C(3) in a pseudoequatorial position.…”

“…This is typical of bicycl0[2.2. llheptane systems [lo] and was confirmed by the I3C-NMR spectra of epoxides 14, 18 (3J(H-C(4), C-C(5)) = 4-5 Hz) and 15,19 ('J(H-C(4), C-C(S)) < 1 Hz; Scheme 2). Compounds 18 and 19 were obtained as a 1 :1.5 mixture on treatment of diene 17 [5] with 1 mol-equiv. of in-ClC,H,CO,H in CH,Cl, (20°C).…”

Condensation of 2,3‐Di(methylidene)‐7‐oxabicyclo[2.2.1]heptane Derivatives into Dicarbonyl[η3:η3‐octa‐2,6‐diene‐1,8‐diyl]iron Complexes with Nonacarbonyldiiron. Crystal Structure of (1RS,2RS,3RS,4SR,5RS,6SR,1′RS,2′RS,3′RS,4′SR,5′RS,6′SR)‐Dicarbonyl‐{(2,3,C‐η:2′,3′,C‐η)‐2,2′‐ethylene‐5,5′,6,6′‐tetrakis[(methanesulfonyloxy)‐methyl]‐3,3′‐di(methylidene)‐bis[7‐oxabicyclo[2.2.1]hept‐2‐yl]}iron

“…-Diene 5 was derived from the Diels-Alder adduct of furan to maleic anhydride via tetrol 11 following a procedure developed earlier in our laboratory [14] (Scheme I). On stirring 5 in hexane with an excess of [Fe,(CO)J at 20" for several days, a mixture was obtained from which the known [Fe(CO),(diene)] complex 7 [15] (72-79 YO) and the new [Febis(allyl)(CO),] complex 9 (4-8 %) could by isolated by column chromatography on silica gel.…”

“…(5) with Nonacarbonyldiiron. A mixture of 5 [14] [I51 (1.06 g, 4.84 mmol) and [Fe2(C0)9] (5.46 g, 15 mmol) in hexane (100 ml) was stirred at r.t. for 87 h. The mixture was filtered through Celite, and the filtrate was purified by column chromatography (CC; silica gel, petroleum ether/CH2C12 gradient). After [Fe(CO),] and [Fe3(C0),2] were eluted with petroleum ether, two yellows bands were separated.…”