Triquinanes angular

Chung and coworkers [280] combined a [2+2+1] with a [2+2+2] cycloaddihon for the synthesis of multi-ring skeletons, angular triquinanes, and fenestranes. For the preparation of tetracyclic compounds such a 6/4-17, these authors used diynes as 6/4-16 and CO as substrates (Scheme 6/4.5). Fully substituted alkynes gave low yields, and 1,5- as well as 1,7-dialkynes, did not react... 

Sequential pyrrolidine and hydantoin ring-forming reactions via intramolecular [2+3] cycloaddition have been applied to the stereoselective solid-phase synthesis of conformationally constrained tricyclic triazacyclopenta [C]pentalene scaffold 43 < 1999JOC8342>. These novel compounds 43 share the structural complexity characteristic of certain alkaloid natural products, angular triquinanes. The retrosynthetic analysis is shown in Scheme 87. 

An intramolecular nitrile oxide cycloaddition also served as the key step in the stereoselective assemblage of the skeleton of angular triquinane sesquiterpenes of the isocomene series. Tetracyclic isoxazoline 203 was obtained from oxime 202 [derived from tetrahydroindandione 201] and on treatment with sodium hypochlorite... 

The aminocarbonylation of alkynes has been less explored as compared to that of alkenyl and (hetero)aryl halides. Nevertheless, several noteworthy applications of this reaction have been reported, including the syntheses of 2-ynamides, chiral 2-carbamoyl-7r-allylic tungsten complexes, angular triquinanes, 2-(carbamoylmethylene)tetrahydrofurans, alle-nyl amides, and others. ... 

Aminocarbonylation has been combined with the Pauson-Khand reaction to construct fused tricyclic alkaloid skeletons (see 00154). The tandem aminocarbonylation/Pauson-Khand reaction of haloalkynes with a chiral allylic amine promoted by Co2(CO)8 gave angular triquinanes as exemplified in Scheme 25. Thus, the reaction of l-chloro-2-phenylethyne 175 with Co2(CO)8 at 0°C gave alkyne-dicobalt complex 176, which was converted to enoyl-dicobalt complex 177 upon warming to 25 °C. The reaction of enoyl-dicobalt complex 177 with cyclopente-nylmethyl(l-phenylethyl)amine 179 yielded Pauson-Khand reaction product, angular triquinane 180, via A -allylic aminocarbonylated alkyne-dicobalt complex 178 (Scheme 25). ... 

Intramolecular tandem Michael reaction.1 Angular triquinane sesquiterpenes such as pentalenene (5) have been synthesized from the bis(enone) 1 by an ntramolecular tandem Michael reaction as the key step for conversion to the rncvclic system. Lithium amides, even bulky ones, are not useful for this step, nor > dimethyl-t-butylsilyl triflate. Annelation can be achieved by reaction of 1 with c lSi(CH3)3, zinc chloride, and N(C2H5), at 160° in either toluene or CH2C12. Use... 

Hudlicky developed a general method of triquinane synthesis based on a cyclopropanation- arrange-ment sequence of dienic diazo ketones (Scheme 52). Topological selectivity of linear versus angular triquinane synthesis has been achieved. ... 

A intramolecular version of this potential process was conducted with equal success. In addition, a formal synthesis of the angular triquinane isocomene was highlighted (Sch. 42) [92],... 

Pattenden and Teague have achieved the total synthesis of the angular triquinane (3) by procedures which include intramolecular 2ir+2Tr photocycloaddition of an enone. 

Scheme 7-59 Access to linear or angular triquinane skeleton.

In an imaginative construction of the angular triquinane ( )-hirsutene (158), Oppolzer and Robyr reported the carbonylative closure of allylic carbonate 155 to yield bicyclooctanes 156 and 157 (Scheme 6-27) [57]. In this multistep transformation, a alJylpalladium intermediate arising from the allylic carbonate 155 undergoes intramolecular Heck insertion of the pendant alkyne. Carbonylation of the resulting vinylpalladium intermediate, another Heck cyclization, and a second carbonylation then provide a mixture of acids, which after esterification yield esters 156 and 157 in good yield. 

In the synthesis of angular triquinane ( )-silphinene by S. Yamamura et al., the Criegee oxidation was used to obtain a key bicyclic intermediate. ... 

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