Regioselectivity and stereospecificity in homoketonizations. Control by thermodynamic and steric factors.

Difunctionalized brendanes via thallium triacetate cleavage of the cyclopropyl ring of triaxane

“…Removal of solvent left a pale yellow oil. Recrystallization from pentane (twice) gave white crystals (16 mg, 38%): mp 86.5-87.5 °C; IR (CCI4) 1751 (s, ester C=0), 1249 cm"1 (s); NMR (CC14) 4.86 8-Acetoxybrendane (19). Ethylene dithioketal 18 (34 mg, combined crystals and mother liquor residue) and activated Raney nickel22b were refluxed in ethanol (13 ml) for 1.5 h. The mixture was filtered through Celite, and water (65 ml) was added.…”

“…Keto acetate 17 was converted to its crystalline ethylene dithioketal 18 and directly desulfurized to give the previously unreported 8-acetoxybrendane (19) in 61% yield. The brendane skeleton in 19 was established as described earlier in Scheme I.…”

Opening the [4 + 2 + 2] Cycloadducts of Bicyclo[2.2.1]hepta-2,5-dienes (Norbornadienes) to Cis-Fused Bicyclo[5.3.0]decanes1

“…Only limited success scattered through the literature has been reported in opening the [2 + 2 + 2] cycloadducts of norbornadiene, and no reports other than our own preliminary communications 4 had dealt with the [4 + 2 + 2] adducts. Nickon had employed acidic conditions to open deltacyclane ( 2 ) to mixtures of brendane ( 3 ) and brexane ( 4 ) acetates with the former dominating (Figure , eq 1), conditions which we had adopted to open other [2 + 2 + 2] adducts as well as a [4 + 2 + 2] cycloadduct 4a, eq 2) .…”

“…More recently, Lautens utilized an Hg(II)-promoted opening to form brendane derivatives from deltacyclanes (Figure , eq 2) . In both cases, subsequent conversion to the corresponding brendanones set the stage for the opening to the biquinanes, Nickon using Haller−Bauer chemistry, 5c, while Lautens followed a Baeyer−Villiger route with reductive opening of the lactone finally achieving the biquinane. Others have also reported the use of Baeyer−Villiger oxidations of brendanones to access biquinanes, though the brendanones were not prepared from deltacyclanes. , We now report the opening of [4 + 2 + 2] homo-Diels−Alder adducts of norbornadienes using either the Nickon conditions or [Pt(C 2 H 4 )Cl 2 ] 2 (Zeise's dimer) 4b to yield the highly functionalized targets: cis-fused bicyclo[5.3.0]decanes.…”

“…Others have also reported the use of Baeyer−Villiger oxidations of brendanones to access biquinanes, though the brendanones were not prepared from deltacyclanes. , We now report the opening of [4 + 2 + 2] homo-Diels−Alder adducts of norbornadienes using either the Nickon conditions or [Pt(C 2 H 4 )Cl 2 ] 2 (Zeise's dimer) 4b to yield the highly functionalized targets: cis-fused bicyclo[5.3.0]decanes.

1 Nickon's acid-catalyzed opening of deltacyclane ( 2 ) to brendyl acetate 3 and brexyl acetate 4 (eq 1) . Lautens' Hg(II)-ptomoted opening of deltacyclanes to brendanes ( Eq 2 )

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