Stannanes reactions with ketones

Allenylsilanes and -stannanes combined with a titanium salt are versatile reagents for propargylation of aldehydes (Eq. 115) [297], ketones (Eq. 116) [298], (A,0)-acetals (Eq. 117) [299], and a,/ -unsaturated ketones in a conjugate fashion (Eq. 118) [300]. Intramolecular reaction has also been reported (Eq. 119) [301] in which a Bu3Sn-carbon bond was cleaved exclusively in the presence of a TBS-carbon bond. That the isomeric starting material, propargylstannane, did not give the desired product (Eq. 120) demonstrates that the direct scission of the carbon-Sn bond by the electrophile under these reaction conditions is not a feasible path [301]. 

In contrast to the inertness of alkyl-silanes and -stannanes, alkylplumbanes in the presence of TiCU add to aldehydes. The effectiveness of BF3 as the promoter eliminates the possibility of organotitanium species occurring as intermediates. Addition of R4Pb to a mixture of an aldehyde and TiCU is important, as clean reaction does not occur when the order of addition is reversed, i.e. addition of the aldehyde to a mixture of R4Pb and TiQ. As the reagent reacts only with aldehydes and not with ketones, octanal can be butylated selectively in the presence of 2-octanone (equation 15). ... 

SET photochemistry is involved in the reaction between the enones (371) and the a-stannyl ethers (372) in methanol. The products are the 3-sub-stituted cycloalkanes (373) which arise from addition of aryloxymethyl radicals to the enones. Irradiation (X > 400 nm) of the stannanes (374) in the presence of the ketones and aldehydes (375) affords two products identified as (376) and (377). The former of these is dominant and the reaction arises by an electron transfer from the stannane to the ketone. The resultant stannane radical-cation undergoes fission to yield an alkoxy allyl radical and the tin cation. The alkoxyalkyl radical adds to the carbonyl radical-anion with a preference for... 

Solid-phase synthesis was initiated by coupling 28 to aminomethylated polystyrene resin 29 in NMP with DIEA as base and DMAP as an acylation catalyst. Stille reactions of the polymer-bound stannane 30 with different aromatic and aliphatic acid chlorides and subsequent cleavage of the Bpoc protecting group by brief treatment with 3% TFA in CHjClj afforded polymer-bound 2-aminoaryl ketones 31 as shown in Scheme 4.1.7. 

The lithium cuprates 39, prepared from a- and P-2-deoxy-D-glucopyranosyl-stannanes a- and P-38 are configurationally stable and provide the corresponding Michael addition products 40 on reaction with methyl vinyl ketone [Eq. (14)] [27]. The cuprates a-39 [28] and 41 [29] have been used by Kocienski et al. for allylic substitution at q -molybdenum complexes. 

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