Allenyl transfer reagents

Allylations, allenylations, and propargylations of carbonyl compounds in aqueous media can also be carried out with preformed organic tin reagent, rather than the use of metals.86,87,88 For example, the allylation reaction of a wide variety of carbonyl compounds with tetraal-lyltin was successfully carried out in aqueous media by using scandium trifluoromethanesulfonate (scandium triflate) as a catalyst (Eq. 8.40).89 A phase-transfer catalyst (PTC) was found to help the allylation mediated by tin at room temperature without any other assistance.90... 

The analogous reactions on ( / -propargyl)Fp and (/3-oxoaUcyl)Fp complexes afford related complexes (79n) and (79o), respectively (Scheme 38). Cationic allenyl iron complexes related to (79o) can also be obtained by protonation of the propargylic species with HBF4 or by transfer of the Fp cation via reagents (79a-c). ... 

A chiral reagent derived from tin(II) catecholate, DBU, allyl bromide, and (+)-di-/-butyl tartrate reacts with aromatic aldehydes in a Cul-catalyzed reaction, giving homoallylic alcohols sometimes in excellent optical purities. Allylation with allyltrichlorosilane has been conducted in the presence of 45 and 46 (cf. allenylation of aliphatic aldehydes ). Allylsilanes modified by a tartrate ester show a range of effectiveness in chirality transfer. ... 

Deprotonation of (1) with lithium diisopropylamide takes a different course (eq 4). The initially formed allenyl anion isomerizes to the acetylide, which is trapped with ketones or aldehydes to produce propargyl alcohols (S). The isomerization is postulated to take place through proton transfer steps mediated by diisopropylamine. This is consistent with the observation that no such isomerization takes place with alkyUithium reagents. The propargyl alcohols (3) are converted to methoxydihydrofurans (4) with catalytic potassium hydride in DMSO. ... 

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