Synthesis Of Triquinanes Research Articles

Diastereoselective Domino Synthesis of Triquinanes

An intramolecular Diels-Alder ­(IMDA)-tandem metathesis strategy is used to access a vinyl triquinane skeleton and a formal synthesis of (±)-Δ9(¹²)-capnellene is realized. A variety of strategies have been applied to the synthesis of similar terpenoids (see Review below) and this sequence is an interesting addition. The authors also present a discussion of two possible metathesis sequences: ring-opening-ring-closing metathesis (ROM-RCM) versus ring-closing-ring-opening-cross-metathesis (RCM-ROM-CM, pictured). Evidence supporting the latter proposal is disclosed.

ChemInform Abstract: Application of Ring Strain in the Synthesis of Triquinanes: Synthesis of Pentalenene and Ventricosene

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

An approach to triquinane synthesis using the Pauson–Khand reaction

Tricyclic skeletons have been generated from acyclic enyne precursors by using an intramolecular Pauson–Khand reaction in combination with aldol, Michael and alkylation reactions.

ChemInform Abstract: Synthesis of Polyfunctionalized Bis‐Anellated Pyranosides: Useful Intermediates for Triquinane Synthesis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of polyfunctionalized bis-annulated pyranosides: Useful intermediates for triquinane synthesis

A mild method for the synthesis of bis-cyclopentanoids on carbohydrate templates using the Pauson-Khand reaction is described.

ChemInform Abstract: A General Solution to the Synthesis of Triquinanes by a Palladium‐ Catalyzed Process.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A general solution to the synthesis of triquinanes by a palladium catalyzed process

A previously described palladium-catalyzed tandem cyclisation leading to linear triquinanes has been generalized by disfavoring the competing Heck reaction. Two structural factors (nature of the nucleophile and of the vinylic halogen) play an important role in this generalization.

ChemInform Abstract: Pd(II)‐Promoted Cyclization in Linear Triquinane Synthesis. Total Synthesis of (.+‐.)‐Hirsutene.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Pd 2+-Promoted cyclization in linear triquinane synthesis total synthesis of (±)-hirsutene

A sequence leading from trans-6-methyl-3-cyclohexenecarboxylic acid ( 3) to the cis, anti, cis - tricyclopentane ring system of the hirsutanes is described in which the key step utilizes an acid catalyzed intramolecular conjugate addition ( 5→6a) and a Pd 2+-promoted highly stereocontrolled cyclization ( 7→8).

The Pauson-Khand reaction in triquinane synthesis: approaches to pentalenene, pentalenic acid, and silphinene

Substituted pentynylcyclopentene precursors for the synthesis of pentalenene, pentalenic acid, and silphinene by intramolecular Pauson-Khand cycloaddition reaction have been prepared from 2-methylcyclopentanone via 5-methylcyclopentenyllithium. Conjugate addition of the latter to BHT methacrylate followed by methylation were the key steps in enyne syntyhesis. Reaction of 4,4-dimethyl-5(5-methylcyclopentenyl)-1-pentyne with Co 2 (CO) 8 produces two diastereomeric triquinane enones in an overall yield of 51%, with the exo-9-methyl isomer predominating by ratio of 8:1. This material was converted into pentalenene in two steps. Pauson-Khand reaction of the TBDMS ether of 4,4-dimethyl-5-(5-methylcyclopentenyl)-1-pentyn-3-ol proceeds in 33%

Intramolecular [2+2] photocycloaddition of N-alkenoyl β - enaminones

Intramolecular cycloaddition of N-alkenoyl β-enaminones occurs with high regioselectivity and diastereoselectivity leading to interesting synthons for the total synthesis of triquinanes or various sesquiterpenes.

Cyclopentanoid allysilanes in synthesis: Generation via intramolecular ene reaction of activated 1,6-dienes and application to the synthesis of functionalized diquinanes

A new general route to cis -1,2-disubstituted cyclopentanoid allylsilanes useful in di-and triquinane synthesis is described based on intramolecular ene reaction of activated 1,6-dienes featuring a homoallylsilane unit as the ene donor.

Bifunctional reagents in organic synthesis. Total syntheses of the sesquiterpenoids (±)-pentalenene and (±)-9-epi-pentalenene

Transformation of the readily available keto acetal 14 into the enone 23 was accomplished via a seven-step sequence of reactions. Reaction of 23 with the bifunctional Grignard reagent 5 in the presence of copper(I) bromide – dimethyl sulfide, followed by intramolecular alkylation of the resultant chloro ketone 24, gave the tetracyclic ketone 25. Treatment of 25 with hydrogen in the presence of platinum afforded a mixture of the ketones 27 and 28 (42:58, respectively), which was transformed into a separable mixture of (±)-pentalenene (1) (32%) and (±)-9-epi-pentalenene (30) (33%). Keywords: ±-pentalenene synthesis, ±-9-epi-pentalenene synthesis, sesquiterpenoid synthesis, methylenecyclopentane annulation, bifunctional reagents, triquinane synthesis.

Intramolecular additions of allylsilanes in triquinane synthesis. Studies directed toward the total synthesis of (±)-hirsutene

The straightforward construction of the cis , anti , cis -cyclopenta[ a ]pentalene skeleton characteristic of (±)-hirsutene was achieved via the intramolecular addition of two functionalized cyclopentane rings linked by a one-carbon tether.

Radical-initiated polyolefinic cyclizations in linear triquinane synthesis. model studies and total synthesis of (±)-hirsutene

Details of a novel radical-initiated polyolefinic cyclization approach to linear condensed cyclopentanoids are reported. The strategy is executed in three stages: (1) Sn2′-anti opening of a vinyl lactone to produce a trans-3,5-disubstituted cyclopentene, (2) rapid elaboration to a cyclization precursor, and (3) single step tandem radical cyclization to produce a cis-anticis tricyclo[3.3.0]undecane. Model substrates 16a and 16b give high yields of tricyclic products 17 and 18 , respectively. An effort to rationalize the interesting endo selectivity via the Beckwith transition state model is proposed. Cyclizations of 28 and 29 to 30 and 31 demonstrate the viability of a tandem hexenyl-hexynyl cyclization. The work culminates with a total synthesis of (±)hirsutene. A selective approach to methyl substituted vinyl lactones by Claisen rearrangement-phenylselenolactonization-elimination of acetoxy cyclopentenols is exemplified by the synthesis of 12 . Tandem cyclization of 38 produces hirsutene ( 1 ) in a single step. Alternatively, cyclization of 37 yields trimethylsilyl hirsutene.

A new approach to all— cis triquinane synthesis and a new route to the C 16—hexaquinane system

A new synthesis of all- cis triquinanes is presented. The examples bear a cis substituent on the fifth position of the central ring, and are thus all- cis pentasubstituted cyclopentanes. The stereo-controlled addition of organometallics of 7-ketonorbornenes is considered, as is “reductive solvolysis” of such adducts to the corresponding hydrocarbons. The preparation of trans-3,4-dimethoxycyclopentyl chloride is given, as is that of the corresponding organolithium. The use of quinoxaline derivatives in aldol-type reactions is considered, with examples. A new approach to the C 16-hexaquinane system is developed. The ring systems reported include: tricyclo-[8.2.1.0 2,9]tridecane, tricyclo[6.3.0.0 3,7]undecane, tetracyclo-[10.1.0.0 2,9.0 10,13]tridecane, pentacyclo[8.5.1.0 2,6.0 7,16.0 11,15]hexadene and hexacyclo(8.5.1.0 2,6.0 3,14.0 7,16.0 11,15]hexadecane.