Highly Stereoselective C–C Bond Formation by Rhodium-Catalyzed Tandem Ylide Formation/[2,3]-Sigmatropic Rearrangement between Donor/Acceptor Carbenoids and Chiral Allylic Alcohols

Abstract

The tandem ylide-formation/[2,3]-sigmatropic rearrangement between donor/acceptor rhodium-carbenoids and chiral allyl alcohols is a convergent C—C bond forming process, which generates two vicinal stereogenic centers. Any of the four possible stereoisomers can be selectively synthesized by appropriate combination of the chiral catalyst Rh2(DOSP)4 and the chiral alcohol.

Scope and Mechanistic Analysis of the Enantioselective Synthesis of Allenes by Rhodium-Catalyzed Tandem Ylide Formation/[2,3]-Sigmatropic Rearrangement between Donor/Acceptor Carbenoids and Propargylic Alcohols

“…We knew from our studies with allyl alcohols, that the [2, 3] sigmatropic rearrangement of the oxonium ylide is favored when the allyl group is more highly substituted. 5 The reaction of 5a with the tertiary propargylic alcohol 6b did result in the formation of the [2, 3]-sigmatropic rearrangement product 8b in 42% yield and 27% ee (entry 2). The racemic O—H insertion byproduct 7b was still formed, albeit in diminished yield (12%).…”

“…These conclusions also help rationalize the similar product distributions trends seen in the reaction of allyl alcohols with donor/ acceptor carbenoids. 5a …”

Highly stereoselective synthesis of cyclopentanes bearing four stereocentres by a rhodium carbene-initiated domino sequence

“…Flash column chromatography was performed with silica gel 60 A (230-400 mesh) according to the literature procedure. 71 Substrates 2 , 72 Rh 2 ( S DOSP) 4 and Rh 2 ( R -DOSP) 4 , 73 16 , 17b–d , 19a and c , 23b , 68 17a , 74 19b , 75 19d , 76 and 23a 77 were all synthesized according to published procedures. For 1 H and 13 C NMR data see Supplementary Figures 3–34.…”

Gold(I)‐Catalysed Direct Thioetherifications Using Allylic Alcohols: an Experimental and Computational Study

“…Although the majority of the products formed by this method are achiral, some of the γ-substituted substrates may be amenable to chirality transfer. In theory, an enantioenriched chiral allylic alcohol with a γ-substituent (such as 18 , entry 12), which is easily accessible in high ee values by Sharpless kinetic resolution[ 18 ] or enzyme resolution,[ 19 ] should be able to transfer its chirality[ 20 ] to the allylic thioether product 3 z , especially if a 6-membered ring H-bonded intermediate is involved. Disappointingly, our initial attempt at chirality transfer with enantioenriched secondary allylic alcohol ( S )- 18 (91:1 e.r.…”

“…Suspecting that the phenyl substituent in 18 is to blame (the phenyl substituent may be stabilising a planar allylic cation intermediate which may be otherwise disfavoured), enantioenriched allylic alcohol ( R )- 21 (94:6 e.r. )[ 19 ] and ( R )- 20 (>99:1 e.r.) were investigated instead.…”