Metalation and silylation of allene: A convenient synthesis of tetrakis(trimethylsilyl)allene

Jaffe, Fred

doi:10.1016/s0022-328x(00)92794-3

Cited by 49 publications

(5 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Absorptions at 1850−1900 cm -1 were assigned to allenyl and >2000 cm -1 to propargyllithium reagents. Allenyllithium has an absorption at 1895 cm -1 . , The metalation product of dicyclopropylacetylene 8P - H was identified as a propargyllithium reagent ( 8P - Li ) on the basis of an IR absorption at 2160 cm -1 . Zinc, boron, titanium, and aluminum allenyl and propargyl structures have also been identified by their IR absorptions. ,15a …”

Section: Introductionmentioning

confidence: 99%

Solution Structure and Stereochemistry of Alkyl- and Silyl-Substituted Allenyl-Propargyllithium Reagents

et al. 1999

View full text Add to dashboard Cite

Analysis of 13 C chemical shifts and Li-C couplings showed that allenyllithium (5A-Li) was a mixture of monomer and dimer in THF, both with an allenyl structure. Similarly, the metalation products of 2-butyne (6A-Li), 4-methylpentyne (9A-Li), and 4,4-dimethylpentyne (21A-Li) in THF, as well as several 1, 3-dialkyl (32A-Li, 33A-Li, 34A-Li) propargyl-allenyllithiums formed by metalation or Li/Sn exchange were all monomeric lithioallenes in THF. Compound 6A-Li was shown to have less than 5% and 21A-Li less than 3% of the propargyllithium isomers (6P-Li, 21P-Li) present from analysis of residual broadening of the propargyl carbon by Li-C coupling. The reagent prepared by metalation of dicyclopropylacetylene (8P-Li) has a propargyl structure, but two related reagents with a cyclobutane spanning the 3,3-positions (37A-Li and 39A-Li) had allenyl structures. Several triorganosilyl-substituted reagents were also investigated. Those with silyl groups at the allenyl position (28A-Li, 31A-Li) are allenyllithiums, those with silyl groups at the propargyl position (22-Li to 26P-Li) showed chemical shifts intermediate between those of allenyl and propargyl isomers, and the shifts were strongly temperature-dependent under some conditions. These compounds are probably equilibrating mixtures of allenyl and propargyllithiums or equilibrating mixtures of unsymmetrically π-complexed structures, with barriers to interconversion (∆G q -150 ) below 4 kcal/mol. Several of the organolithium reagents studied had diastereotopic carbon signals (SiMe 2 , CMe 2 , or CPh 2 groups), which allowed determination of barriers to configurational inversion of the chiral allenyl fragment. Barriers from 6.1 kcal/mol (26A-Li in dimethyl ether) to 14.5 kcal/mol (39A-Li in 3:2 THF/ether) were measured.

show abstract

Section: Introductionmentioning

confidence: 99%

Solution Structure and Stereochemistry of Alkyl- and Silyl-Substituted Allenyl-Propargyllithium Reagents

et al. 1999

View full text Add to dashboard Cite

show abstract

“…It should be, however, stressed that the existence of a 1,1-dilithioallene derivative has not yet been proved unequivocally. For example, dilithiation of allene gives a dilithium derivative, which after trapping with Me 3 SiCl yields 1,3-bis(trimethylsilyl)propyne . Similarly, reaction of 3-trimethylsilyl-3-ethoxycarbonylcyclopropene ( 1 ) with LDA/TMEDA at −60 to −30 °C, followed by addition of Me 3 SiCl, affords ethyl 4-trimethylsilyl-3-butynoate 3c…”

Section: Resultsmentioning

confidence: 99%

Novel Organogermanium Compounds via Metalation of 3-Trimethylsilyl-3-ethoxycarbonylcyclopropene Derivatives

2004

View full text Add to dashboard Cite

show abstract

“…Despite these advances,e stablished methods require low reaction temperatures to avoid substrate epimerization when applied to carbonyl substrates with a-stereogenic centers. Although allenyllithium has been prepared at À78 8 8C, [6] it is generally considered as unstable,w hich limits its application in organic synthesis.I na ddition, handling allene gas in batch also poses many practical challenges. [5] Theu se of mercury,t he corrosiveness of propargyl bromide,a nd the pyrophoric nature of the allenyl boronic acid raise significant environmental and safety concerns when using these reagents for large-scale applications.T he direct lithiation of allene, ar eadily available and inexpensive starting material, is ap otential alternative to propargyl bromide magnesiation if apractical lithiation/transmetallation process could be developed.…”

mentioning

confidence: 99%

“…[5] Theu se of mercury,t he corrosiveness of propargyl bromide,a nd the pyrophoric nature of the allenyl boronic acid raise significant environmental and safety concerns when using these reagents for large-scale applications.T he direct lithiation of allene, ar eadily available and inexpensive starting material, is ap otential alternative to propargyl bromide magnesiation if apractical lithiation/transmetallation process could be developed. Although allenyllithium has been prepared at À78 8 8C, [6] it is generally considered as unstable,w hich limits its application in organic synthesis.I na ddition, handling allene gas in batch also poses many practical challenges.Continuous-flow synthesis has evolved into important technology in fine chemical and pharmaceutical research, development and manufacturing. [7] Advantages such as rapid mixing and efficient heat transfer of flow technologies allow access to chemistries involving highly reactive or short-lived intermediates,and chemistries difficult or impossible to scale using standard batch vessels.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Flow Asymmetric Propargylation: Development of Continuous Processes for the Preparation of a Chiral β‐Amino Alcohol

Sheeran

Clausen

et al. 2017

Angew Chem Int Ed

View full text Add to dashboard Cite

The development of a flow chemistry process for asymmetric propargylation using allene gas as a reagent is reported. The connected continuous process of allene dissolution, lithiation, Li-Zn transmetallation, and asymmetric propargylation provides homopropargyl β-amino alcohol 1 with high regio- and diastereoselectivity in high yield. This flow process enables practical use of an unstable allenyllithium intermediate. The process uses the commercially available and recyclable (1S,2R)-N-pyrrolidinyl norephedrine as a ligand to promote the highly diastereoselective (32:1) propargylation. Judicious selection of mixers based on the chemistry requirement and real-time monitoring of the process using process analytical technology (PAT) enabled stable and scalable flow chemistry runs.

show abstract

Metalation and silylation of allene: A convenient synthesis of tetrakis(trimethylsilyl)allene

Cited by 49 publications

References 30 publications

Solution Structure and Stereochemistry of Alkyl- and Silyl-Substituted Allenyl-Propargyllithium Reagents

Solution Structure and Stereochemistry of Alkyl- and Silyl-Substituted Allenyl-Propargyllithium Reagents

Novel Organogermanium Compounds via Metalation of 3-Trimethylsilyl-3-ethoxycarbonylcyclopropene Derivatives

Flow Asymmetric Propargylation: Development of Continuous Processes for the Preparation of a Chiral β‐Amino Alcohol

Contact Info

Product

Resources

About