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Alkylation boron stabilized carbanions

In general, all types of boron-stabilized carbanions are readily alkylated by primary alkyl halides. The situation for the i ylation of dimesitylboryl compounds is sununarized in Scheme 2. These reactions represent highly efficient homologation processes. Oxidation of the tertiary all l organoboranes is slow, but use of 4-methoxy-2,6-dimethylphenyl groups instead of mesityl groups renders the products sensitive to solvolysis. ... [Pg.495]

Alkylations of boron-stabilized carbanions have been carried out with primary alkyl halides containing acetal, alkene, alkyne, chloride, cyano, ester and tosylate groups, though a ketone group was not tolerated. ... [Pg.495]

Rathice and Kow first reported the preparation of a boron-stabilized carbanion by direct deprotonation of the carbon acid. They made the important observation that the deprotonation needed a sterically demanding base to prevent its complexation with boron. Thus the anion of B-methyl-9-borabicy-clo[3.3.1]nonane, prepared by deprotonation with lithium 2,2,6,6-tetramethylpiperidine (LiTMP) in benzene, can be alkylated successfully. [Pg.199]

Matteson and coworkers have described the deprotonation and alkylation of bis(l,3,2-dioxaborin-2-yOmethane (11). Deprotonation with LiTMP yields the stabilized anion, which can be alkylated with a variety of primary alkyl halides. Oxidation under basic conditions then unmasks the carbonyl group. Matteson has also described the deprotonation of some substituted boronic esters (12 X = SPh, SiMei). - The alkylated products derived from (12 X = SPh) can be treated with A/-chlorosuccinimide under mild basic conditions to yield either the monothioacetals or the acetals. Boron-stabilized carbanions can also be generated by transmetallation of the organostannanes. ... [Pg.199]

Corey et al have elegantly exploited the ability of oxime ethers to stabilize carbanions syn to the N-alkoxy substituent in the boron trifluoride mediated addition of the mixed cuprate reagent derived from (177) to a,3-unsaturated oxime ether (178 Scheme 34). Stereochemistry is established by the ring r-bu-tyldimethylsiloxy group. The addition does not occur in the absence of boron tiifluoride. The alkylation of the cuprate adduct of (178) by iodoalkyne (179) provides the PGEj skeleton. [Pg.386]

A treatment of 314 with LDA yielded a carbanion stabilized by boron and sulfur atom, which undergoes alkylation with organic halides and with methyl acrylate (Equation (93)).473... [Pg.185]

This chapter deals with the formation of new C—C bonds by alkylation of sp -hybridized carbanions stabilized by a range of heteroatoms, including oxygen, boron, silicon, phosphorus and the halogens. The properties of the same carbanions with additional stabilization provided by an adjacent double bond are also discussed. [Pg.193]


See other pages where Alkylation boron stabilized carbanions is mentioned: [Pg.320]    [Pg.320]    [Pg.184]    [Pg.848]    [Pg.848]    [Pg.10]    [Pg.52]    [Pg.15]   
See also in sourсe #XX -- [ Pg.495 ]

See also in sourсe #XX -- [ Pg.495 ]

See also in sourсe #XX -- [ Pg.495 ]




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Alkyl boron

Alkyl boronates

Alkylation boron stabilized

Alkylation carbanion

Alkyls stability

Boron-stabilized

Boron-stabilized carbanions

Boronates stability

Carbanions alkyl

Carbanions alkylation

Carbanions alkylations

Stabilized carbanion

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