Stille cross-coupling of activated alkyltin reagents under "ligandless" conditions
(Chemical Equation Presented) Monoalkyltins activated by a fluoride source are shown to be as reactive as their vinyl or aryl homologues in the Stille coupling reaction, thus providing an easy entry into the pallado-catalyzed formation of Csp3-Csp2 bonds. In addition to this uncommon reactivity, this methodology holds several advantages such as (i) a quantitative preparation of stable and easy to handle alkyltin reagents 2, (ii) a simplified coupling procedure without any phosphine added ligand under neutral conditions, and (iii) a facile purification step of the organic products from the inorganic nontoxic tin byproducts.
Herve, Agnes,Rodriguez, Alain L.,Fouquet, Eric
p. 1953 - 1956
(2007/10/03)
Synthesis of functionalized long-chain thiols and thiophenols for the formation of self-assembled monolayers on gold
The terminally 2-thienyl- and phenyl-substituted eicosane derivatives 4 and 5 were prepared by reacting 1-[(20-bromoeicosyl)oxy]-4-methoxybenzene (3) with 2-lithiothiophene and lithium diphenylcuprate, respectively. Reaction of 4 and 5 with BBr3 leads to the corresponding bromides 6, 7 which afforded the aryl-substituted eicosanethiols 8 and 9 by nucleophilic substitution with thiourea. 4-Eicosylthiophenol (13) was prepared from eicosylbenzene (11) by chlorosulfonation and subsequent reduction of the sulfonyl chloride. Synthesis of the thiol 22 with phenylenedioxy groups incorporated in the alkyl chain involves formation of 19 from allyloxy(bromobutoxy)benzene (18) and (4-(2-thienyl)butoxy)phenol (17). Hydroboration of 19 yields the corresponding alcohol 20, which under Mitsunobu conditions and subsequent reduction with LiAlH4 can be transformed to 22.
Buckel, Frank,Persson, Per,Effenberger, Franz
p. 953 - 958
(2007/10/03)
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