Carbocyclic cis-[1.1.1]-tris-σ-homobenzenes - Syntheses by triple epoxide → cyclopropane conversions, structural data, [σ2s+σ2s+σ2s] cycloreversions
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in: Liebigs Annalen - recueil, Jahrgang 1997, Nr. 5, 01.05.1997, S. 967-989.
Publikation: Beiträge in Zeitschriften › Zeitschriftenaufsätze › Forschung › begutachtet
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T1 - Carbocyclic cis-[1.1.1]-tris-σ-homobenzenes - Syntheses by triple epoxide → cyclopropane conversions, structural data, [σ2s+σ2s+σ2s] cycloreversions
AU - Rücker, Christoph
AU - Müller-Bötticher, Hermann
AU - Braschwitz, Wolf-Dieter
AU - Prinzbach, Horst
AU - Reifenstahl, Uwe
AU - Irngartinger, Hermann
PY - 1997/5/1
Y1 - 1997/5/1
N2 - By triple epoxide → cyclopropane transformation starting from cis-benzene trioxide the 3α,6α,9α-tris(TIPS-ethynyl) (1b), -tris(alkoxycarbonyl) (1d, e), -tricyano (1f), and -tris(ammoniomethyl) (1j) derivatives of the still elusive parent cis-[1.1.1]-tris-σ-homobenzene (1a) have been synthesized. Out of a number of carbon nucleophiles tested, a weakly basic mixed cyanocuprate of Li-TIPS-propyne proved the reagent of choice: Eliminations were largely avoided, the scyllo [*]-2,4,6-tris(TIPS-propargyl)cyclohexane-1,3,5-triol (13a), obtained in a stereoselective one-pot threefold epoxide opening (up to 69%), allowed the pertinent functional group manipulations. The selectivity of the base-induced triple cyclopropane ring closure in the flexible cyclohexane precursors strongly depends on the activating groups and is promoted by fixation of the "all-axial" conformation as an adamantoid orthophosphate. The ΔG ≠ values determined for the generally neat 3σ → 3π isomerizations [28.5 (1e), 29.0 (1f), 22.6 (1j) kcal mol -1] are in line with concerted reaction courses ([σ2s+σ2s+σ2s]). For the trinitrile 1f an X-ray structure analysis confirmed a nearly planar cyclohexane ring and a relatively large cyclohexane/cyclopropane interplanary angle (113°).
AB - By triple epoxide → cyclopropane transformation starting from cis-benzene trioxide the 3α,6α,9α-tris(TIPS-ethynyl) (1b), -tris(alkoxycarbonyl) (1d, e), -tricyano (1f), and -tris(ammoniomethyl) (1j) derivatives of the still elusive parent cis-[1.1.1]-tris-σ-homobenzene (1a) have been synthesized. Out of a number of carbon nucleophiles tested, a weakly basic mixed cyanocuprate of Li-TIPS-propyne proved the reagent of choice: Eliminations were largely avoided, the scyllo [*]-2,4,6-tris(TIPS-propargyl)cyclohexane-1,3,5-triol (13a), obtained in a stereoselective one-pot threefold epoxide opening (up to 69%), allowed the pertinent functional group manipulations. The selectivity of the base-induced triple cyclopropane ring closure in the flexible cyclohexane precursors strongly depends on the activating groups and is promoted by fixation of the "all-axial" conformation as an adamantoid orthophosphate. The ΔG ≠ values determined for the generally neat 3σ → 3π isomerizations [28.5 (1e), 29.0 (1f), 22.6 (1j) kcal mol -1] are in line with concerted reaction courses ([σ2s+σ2s+σ2s]). For the trinitrile 1f an X-ray structure analysis confirmed a nearly planar cyclohexane ring and a relatively large cyclohexane/cyclopropane interplanary angle (113°).
KW - Chemistry
KW - cis-[1.1.1]-Tris-σ-homobenzenes
KW - Substituent effects
KW - [σ2s+σ2s+σ2s] Cycloreversions
UR - http://www.scopus.com/inward/record.url?scp=0345970701&partnerID=8YFLogxK
UR - https://www.mendeley.com/catalogue/62c3684d-30b2-34a8-a4a9-30ffb3d7f993/
U2 - 10.1002/jlac.199719970528
DO - 10.1002/jlac.199719970528
M3 - Journal articles
VL - 1997
SP - 967
EP - 989
JO - Liebigs Annalen - recueil
JF - Liebigs Annalen - recueil
SN - 0947-3440
IS - 5
ER -