Tricyclo undecane synthesis

The di-rc-methane rearrangement is also a convenient way of obtaining polycyclic fused ring systems as illustrated in the synthesis of a tricyclo-undecane (3.17) 327). In the irradiation of dihydrotriquinacene the initial bonding scheme is identical as in (3.14) but ultimate cyclopropane formation is hindered by structural reasons (3.18) 328). 

The synthesis of fUido-tricyclo[4.4.0.02 5]deca-3,8-dien-7,10-dione and verification of its endo-configuration has been reported earlier.3 This adduet is a useful starting material for the syntheses of tetracyclo-[5.3.0.02 6.03 10]deca-4,8-diene,s tricyclo[4.4.0.02 5]deca-3,7,9-triene,6 cis, syn, cjs-tricyclo[5.3.0.02,6]deca-4,8-dien-3,10-dione,7 and 4-oxahexa-cyclo[5.4.0.02 6.03 10.05 9.08,11]undecane.a... 

Lei, B. and Fallis, A.G. 1993. Cycloaddition routes to tricyclo[5.4.01,7.02,9] undecanes A direct total synthesis of (-H)-longifolene via an intramolecular Diels-Alder strategy. Journal of Organic Chemistry, 58 2186-95. 

M. ihara and co-workers utilized an intramolecular double Michael addition for the efficient and completely stereoselective construction of the tricyclo[6.3.0.0 ]undecan-10-one framework during the total synthesis of (+)-longiborneol. The substituted cyciopentenone precursor was exposed to several different reaction conditions, and the highest yield was obtained when LHMDS was used as the base. The first deprotonation took place at C11 the resulting enolate added to C9, and the ester enolate (negative charge located at CIO) in turn added to the cyciopentenone at C3. 

Takasu, K., Mizutani, S., Noguchi, M., Makita, K., lhara, M. Total Synthesis of ( )-Culmorin and ( )-Longiborneol An Efficient Construction of Tricyclo[6.3.0.03,9]undecan-10-one by Intramolecular Double Michael Addition. J. Org. Chem. 2000, 65, 4112-4119. 

The excision of the keto bridge present in tricyclo[5.3.1.1 ]dodecan-l 1-one taken from the work of Cha et al. on synthetic studies of taxol deserves special mention. Highly functionalized derivatives of bicyclo]5.3.1]undecane are obtained using the DIB/I2 system (Eq. 11) [38]. The fragmentation of a related derivative of oxabicyclo[3.3.1]nonan-9-one is used by the same authors as a key step in the synthesis of cK-2,8-disubstituted oxocanes (Eq. 12) [39]. 

Interesting synthetic approaches for the construction of the tricyclo[5.2.2.0k5]undecane skeleton of the eremanes have been developed, but only two have been successful. The synthesis of ( )-eremolactone relied on an acid-catalysed double Michael addition on the silyloxydiene (Scheme 45) (127). This on treatment with mesityl oxide in the presence of titanium (IV) chloride gave, inter alia, an inseparable 1 2 mixture of diastereisomers (189) in 64% yield. Reduction with NaBH4 gave the separable hydroxy ketones (190 and 191, 1 2), the relative stereochemistry of which was secured from an X-ray study of 190. Following the introduction of the double bond, the side chain was elaborated on each of the two diastereoisomers as shown in Scheme 45. This synthesis has a number of problems. A complex mixture of isomers is generated in the first step, the cyclohexene... 

The iV-phenylmaleimide derivative (518), prepared in two steps from a-pyrone and nitrosobenzene, is a dienophile and yields the cycloaddition product (519) on reaction with cyclohexa-l,3-diene." ° The sealed-tube reaction of anthracene with excess l,2-dibromo-3,3-difluorocyclopropene at 120°C gave the crystalline adduct (520), presumably by way of intermediate (521) the mechanism is not known. A synthesis of the tricyclo[5,2,2,0 ]undecane skeleton related to isoeremolactone has been reported. The Diels-Alder adduct (522) was a key intermediate in this synthesis, being converted in two standard steps into an epimeric mixture of compounds... 

SCHEME 20.35. The transannular radical cyclization in the synthesis of tricyclo[6.3.0.0 undecanes. 

Barrero AF, Herrador MM, Quilez del Moral JF, Arteaga P, Sanchez EM, Arteaga JF, Piedra M. Transannular cyclization of epoxycaryophyUenes catalyzed by Ti an efficient synthesis of tricyclo[6.3.0.0 ]undecanes. Eur. J. Org. Chem. 2006 3434-3441. 

In principle, several approaches to the complex tricyclo[5-3-l 0 ] undecane skeleton of seychellene can be devised by strategic bond disconnection. The synthesis by Piers et al. illustrates one of these approaches involving the base-catalyzed intramolecular cyclization of a suitably functionalized c/s-decalone (B) to norseychellanone. 

Singh, V., Samanta, B., and Kane, V.V., Molecular complexity from aromatics synthesis and photoreaction of endo-tricyclo[5.2.2.0 > ]undecanes. Formal total syntheses of ( )- coriolin. Tetrahedron, 56, 7785, 2000. 

Singh, V. and Sharma U., Synthesis and photoreaction of tricyclo[5.2.2.02 ]undecanes in excited singlet ( S) state a novel and stereospecific route to protoiUudanoids,/. Chem. Soc., Perkin Trans. 1, 305, 1998. 

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