Stannylaled benzofuran

In the total synthesis of moracin M (61), a phytoalexin isolated from infected white mulberry, Widdowson et al. first prepared 2-stannylated benzofuran 58 from benzofuran 57 via direct metalation and treatment with Me3SnCl [57], Stannane 58 was then coupled with aryl iodide 59 to afford adduct 60, which was desilylated to moracin M (61). 

Reactions with aryl halides have been described [79-81] in one case a stannylated benzofuran was allowed to react with an aryl iodide containing sterically demanding trialkylsiloxy groups in positions 3 and 5, but yields remained good to excellent [82]. Yang and Wong have also reported coupling reactions of 3,4-bis(tributylstannyl)furan [83,84] (Scheme 4-28). 

The DFT study of the 3 + 2-cycloaddition between ketene and TV-silyl-, IV-germyl-, and TV-stannyl-imines shows that the TV-germylimine reaction is a two-step process the TV-stannylimine reaction is a competition between two- and three-step processes whereas the TV-silyl process follows a three-step process44 A new and convenient synthesis of functionalized furans and benzofurans based on 3 + 2-cycloaddition/oxidation has been reported. The cyclization of cyclic 1,3-bis-silyl enol ethers (48) with l-chloro-2,2-dimethoxyethane (49), via a dianion, produced 5,6-bicyclic 2-alkylidenetetrahydrofurans (50), which are readily oxidized with DDQ to 2,3-unsubstituted benzofurans (51) (Scheme 13)45 The Evans bis(oxazoline)-Cu(II) complex catalyses the asymmetric 1,3-dipolar cycloaddition of a -hydroxyenones with nitrones to produce isoxazolidines.46 The... 

Jousseaume et al. reacted stannylfurans containing an aldehyde substituent in the 2-,3-, or 4-position with chloroforraates [86]. Liebeskind and Wang carried out annelations of furan, thiophene and benzofurans by coupling stannyl derivatives with chlorocyclobutenones [87] (Scheme 4-29). 

---