In situ preparation of (.mu.-chloro)(.mu.-methylene)bis(cyclopentadienyl)(dimethylaluminum)titanium (Tebbe's reagent)

Cannizzo, Louis F.; Grubbs, Robert H.

doi:10.1021/jo00213a040

Cited by 98 publications

(33 citation statements)

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“…The relative configuration of each scaffold obtained from the Diels-Alder reactions (Scheme 3), with the exception of 14c, was established unequivocally through X-ray crystallographic analysis (see the Supporting Information). The structure of 14c was established based on 1 H, 13 C, DEPT, and COSY NMR spectroscopic and mass spectrometric data. In addition, compound 14c, when left at room temperature for over 6 months, was converted into its isomer 14c , which features its enol ether double bond in conjugation with the benzoquinone motif (compare with compound 10a); the X-ray diffraction data of the crystalline solid 14c provided the relative configuration of compound 14c.…”

Section: Resultsmentioning

confidence: 99%

Diversity Through a Branched Reaction Pathway: Generation of Multicyclic Scaffolds and Identification of Antimigratory Agents

Wang

Castellano

Kinderman

et al. 2010

Chemistry A European J

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A library of 91 heterocyclic compounds composed of 16 distinct scaffolds has been synthesized through a sequence of phosphine-catalyzed ring-forming reactions, Tebbe reactions, Diels–Alder reactions, and, in some cases, hydrolysis. This effort in diversity-oriented synthesis produced a collection of compounds that exhibited high levels of structural variation both in terms of stereochemistry and the range of scaffolds represented. A simple but powerful sequence of reactions thus led to a high-diversity library of relatively modest size with which to explore biologically relevant regions of chemical space. From this library, several molecules were identified that inhibit the migration and invasion of breast cancer cells and may serve as leads for the development of antimetastatic agents.

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Section: Resultsmentioning

confidence: 99%

Diversity Through a Branched Reaction Pathway: Generation of Multicyclic Scaffolds and Identification of Antimigratory Agents

Wang

Castellano

Kinderman

et al. 2010

Chemistry A European J

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“…After initial experiments using relatively non-basic methylenedianion equivalents such as the Takai-Nozaki reagent, 94 the Tebbe reagent 95 buffered with pyridine to avoid any C36-epimerization proved superior in this transformation. The Tebbe reagent could conveniently be prepared in situ from Cp 2 TiCl 2 and AlMe 3 92 and afforded the desired olefinated product in 58% yield along with 41% of the recovered ketone. 93 The yield for this step could be elevated to 78% after two recycles.…”

Section: Resultsmentioning

confidence: 99%

Total Synthesis of (+)-Azaspiracid-1. An Exhibition of the Intricacies of Complex Molecule Synthesis

et al. 2008

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The synthesis of the marine neurotoxin azaspiracid-1 has been accomplished. The individual fragments were synthesized by catalytic enantioselective processes: A hetero-Diels-Alder reaction to afford the E- and HI-ring fragments, a carbonyl-ene reaction to furnish the CD-ring fragment, and a Mukaiyama aldol reaction to deliver the FG-ring fragment. The subsequent fragment couplings were accomplished by aldol and sulfone anion methodologies. All ketalization events to form the non-acyclic target were accomplished under equilibrating conditions utilizing the imbedded configurations of the molecule to adopt one favored conformation. A final fragment coupling of the anomeric EFGHI-sulfone anion to the ABCD-aldehyde completed the convergent synthesis of (+)-azaspiracid-1.

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“…With all reactive functionalities in the molecule thus protected, the stage was set for the olefination of the C26‐ketone. The Tebbe reagent,22 buffered with pyridine to avoid any C36‐epimerization, proved to be best in this transformation, and could conveniently be prepared in situ from Cp 2 TiCl 2 and AlMe 3 23 to give the desired olefinated product in 78 % overall yield 24. The key NOE interactions of the spiroaminal portion remained unchanged from those depicted in Figure 2, thus verifying that no potential epimerization at C36 had taken place during these latter transformations.…”

Section: Methodsmentioning

confidence: 99%

Total Synthesis of (+)‐Azaspiracid‐1. Part II: Synthesis of the EFGHI Sulfone and Completion of the Synthesis

et al. 2007

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Dedicated to Professor Dieter Seebach on the occasion of his 70th birthdayWith a practical synthesis of the ABCD aldehyde in hand (2, Scheme 1), [1] herein we describe our progress that culminated in the synthesis of (+)-azaspiracid-1 (1) in 26 linear steps and 2.7 % overall yield.As outlined in Scheme 1, the addition of an anomeric sulfone anion derived from 3 to a C20-electrophile, as represented by aldehyde 2, could provide a highly convergent approach to the target. Since all nine rings of azaspiracid-1 (1) are formed prior to this final fragment coupling, the number of manipulations required after the coupling step would be minimal. Such anomeric sulfone anion additions have considerable precedent, both in the original investigations of anomeric sulfone anions derived from carbohydrates [2, 3] and subsequently in advanced fragment couplings in total synthesis, [4][5][6] although the crucial sulfone anion addition of 3 to electrophiles such as aldehyde 2 would represent the most complex anomeric sulfone anion addition to date.Conformational analysis of the HI spiroaminal portion of pentacyclic sulfone 3 (Figure 1) suggests, on the basis of anomeric stabilization and an analysis of steric effects, that this synthon exists in its favored configuration. Therefore, a number of ketalization events were incorporated into the assembly of 3, in which the molecule is anticipated to spontaneously form the desired tetracyclic FGHI system under equilibrating conditions. The fragment couplings to construct intermediate 4 (Scheme 1) would involve a boronmediated addition of the C27-methyl ketone of the FG ring fragment 6 to the E ring aldehyde 5, while a chelatecontrolled Mukaiyama aldol addition [7] of the enolsilane derived from the C35-methyl ketone of 7 to the aldehyde of 6 was anticipated to establish the stereocenter at C34. By inspection, two syn 1,3-dimethyl synthons of the same configuration are embedded in the azaspiracid structure in the E and the I rings. We were attracted to the possibility of constructing both of these subunits from the common

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In situ preparation of (.mu.-chloro)(.mu.-methylene)bis(cyclopentadienyl)(dimethylaluminum)titanium (Tebbe's reagent)

Abstract: The titanium alkylidene 1 (Tebbe's reagent) is a versatile methylenation agent for the conversion of ketones to olefins and esters to vinyl ethers (eq l).1 Unfortunately, this commercially available reagent (Strem, Alfa) is exf Contribution No. 7126.

Cited by 98 publications

References 0 publications

Diversity Through a Branched Reaction Pathway: Generation of Multicyclic Scaffolds and Identification of Antimigratory Agents

Diversity Through a Branched Reaction Pathway: Generation of Multicyclic Scaffolds and Identification of Antimigratory Agents

Total Synthesis of (+)-Azaspiracid-1. An Exhibition of the Intricacies of Complex Molecule Synthesis

Total Synthesis of (+)‐Azaspiracid‐1. Part II: Synthesis of the EFGHI Sulfone and Completion of the Synthesis

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