80277-60-7Relevant academic research and scientific papers
Highly diastereoselective and enantiospecific allylation of ketones and imines using borinic esters: Contiguous quaternary stereogenic centers
Chen, Jack L.-Y.,Aggarwal, Varinder K.
supporting information, p. 10992 - 10996 (2015/03/30)
3,3-Disubstituted allylic boronic esters are not sufficiently reactive to react with ketones and imines. However they can be converted into the corresponding borinic esters by the sequential addition of nBuLi and TFAA. These reactive intermediates possess
Highly stereoselective C-C bond formation by rhodium-catalyzed tandem ylide formation/[2,3]-sigmatropic rearrangement between donor/acceptor carbenoids and chiral allylic alcohols
Li, Zhanjie,Parr, Brendan T.,Davies, Huw M. L.
supporting information; experimental part, p. 10942 - 10946 (2012/08/07)
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.
Modulating the stereochemical outcome of the Ireland-Claisen reaction of (E)- and (Z)-allylic glycolates
Feldman, Ken S.,Selfridge, Brandon R.
supporting information; experimental part, p. 825 - 828 (2012/03/09)
The diastereoselectivity of Ireland-Claisen rearrangements of allylic glycolates is dependent on the E:Z ratio of the silyl ketene acetals, the alkene geometry in the allyl unit, and the transition state topography. High yields and excellent diastereoselectivities (>95:5) have been achieved for selected substrates, including those with R2 = ethyl that results in a newly formed quaternary center. A discussion of the scope, selectivities, and transition state models will be presented.
Preparation of stereodefined homoallylic amines from the reductive cross-coupling of allylic alcohols with imines
Chen, Ming Z.,McLaughlin, Martin,Takahashi, Masayuki,Tarselli, Michael A.,Yang, Dexi,Umemura, Shuhei,Micalizio, Glenn C.
supporting information; experimental part, p. 8048 - 8059 (2011/02/26)
Regio-, diastereo-, and enantioselective coupling reactions between imines and allylic alcohols have been developed. These coupling reactions deliver complex homoallylic amine products through a convergent C-C bond forming process that does not proceed through intermediate allylic organometallic reagents. In general, convergent coupling, by exposure of an allylic alkoxide to a preformed Ti-imine complex, occurs with allylic transposition in a predictable and stereocontrolled manner. While simple diastereoselection in these reactions is high, delivering anti-products with ≥20:1 selectivity, the organometallic transformation described is compatible with a diverse range of functionality and substrates (including aliphatic and aromatic imines, allylic silanes, trisubstituted alkenes, vinyl- and aryl halides, trifluoromethyl groups, thioethers, and aromatic heterocycles). Alkene geometry of the products is a complex function of the allylic alcohol structure and is consistent with a mechanistic proposal based on syn-carbometalation followed by syn-elimination by way of a boat-like transition state geometry. Single asymmetric coupling reactions provide a means to translate the stereochemical information of the allylic alcohol to the homoallylic amine or to control diastereoselection in the coupling reactions of achiral allylic alcohols with chiral imines. Double asymmetric coupling reactions are also described that afford a unique means to control stereoselection in these complex convergent coupling processes. Finally, empirical models are proposed that are consistent with the observed stereochemical course of these coupling reactions en route to chiral homoallylic amines possessing di- or trisubstituted alkenes and anti- or syn- relative stereochemistry at the allylic and homoallylic positions.
An optimised and recoverable tartrate surrogate for sharpless asymmetric epoxidations
Knight, David W.,Morgan, Ian R.
scheme or table, p. 35 - 38 (2009/05/07)
The tetrahydroxy diester 7d (R = iPr) is almost as effective as diisopropyl tartrate in SAE reactions of (E)-allylic alcohols and can be recovered and re-used following a relatively simple work-up procedure.
Formation of chiral quaternary carbon stereocenters using silylene transfer reactions: Enantioselective synthesis of (+)-5-epi-acetomycin
Calad, Stacie A.,Woerpel
, p. 1037 - 1040 (2008/02/01)
(Chemical Equation Presented) Chiral quaternary carbon stereocenters can be established with high diastereoselectivity by a silylene transfer/lreland- Claisen rearrangement. The utility of this method was demonstrated by application to a synthesis of (+)-
Synthesis of vinyl 1,2-diketones
Habel, Lothar W.,De Keersmaecker, Sigrid,Wahlen, Joos,Jacobs, Pierre A.,De Vos, Dirk E.
, p. 4057 - 4059 (2007/10/03)
A new route is outlined for preparation of vinyl 1,2-diketones via a three-step sequence. First, allylic alcohols are photooxidized by 1O2 to hydroperoxides, which are reduced to vinyl 1,2-diols. These vinyl 1,2-diols are oxidized to vinyl 1,2-diketones with oxoammonium salts, which are prepared in situ from organic nitroxyl radicals. The new route is short, avoids the use of protecting groups, and is generally applicable to obtain aliphatic or aromatic vinyl 1,2-diketones.
Stereoselective reactions of acyclic allylic phosphates with organocopper reagents
Belelie,Chong
, p. 5552 - 5555 (2007/10/03)
A series of acyclic allylic alcohols of general structure R1CH=CHCH(OH)R2 were resolved by Sharpless kinetic resolution. The hydroxyl groups of these enantiomerically enriched alcohols were derivatized to diethyl phosphates, and the derivatives were reacted with organocopper reagents. Cleanest substitution reactions were observed with reagents R32CuCNLi2. With R1 = Me and R3 = n-Bu, the size of R2 affected both the regioselectivity and stereoselectivity of the displacement. Larger R2 groups gave higher regio- and stereoselectivities: with R2 = 3-pentyl, >98% SN2′ regioselectivity and > 98% anti stereoselectivity were observed. Bn2CuCNLi2 gave stereoselectivities comparable to those observed with n-Bu2CuCNLi2 but t-Bu2CuCNLi2 exhibited much lower diastereofacial preference.
A Regioselective and Stereospecific Synthesis of Allylsilanes from Secondary Allylic Alcohol Derivatives
Fleming, Ian,Higgins, Dick,Lawrence, Nicholas J.,Thomas, Andrew P.
, p. 3331 - 3350 (2007/10/02)
Primary and secondary allylic acetates and benzoates react with the dimethyl(phenyl)silyl-cuprate reagent to give allylsilanes, provided that the THF in which the cuprate is prepared is diluted with ether before addition of the allylic ester.The reaction is reasonably regioselective in some cases: (i) when the allylic system is more-substituted at one end than the other, as in the reactions 4->5 and 9->10; (ii) when the steric hindrance at one end is neopentyl-like, as in the reactions 15->16; and (iii) when the disubstituted double bond has the Z configuration, as in th e reactions Z-19->E-21 or, better, because the silyl group is becoming attached to the less-sterically hindered end of the allylic system, Z-20->E-22.The regioselectivity is better if a phenyl carbamate is used in place of the ester, and a three-step protocol assembling the mixed cuprate on the leaving group is used, as in the reactions 23->24 and E- or Z-29->E-21, or, best of all, because the silyl group is again becoming attached to the less-sterically hindered end of the allylic system, E- or Z-30->E-22.This sequence works well to move the silyl group onto the more substituted end of an allyl system, but only when the move is from a secondary allylic carbamate to a tertiary allylsilane, as in the reaction 38->39.Allyl(trimethyl)silanes can be made using alkyl- or aryl-cuprates on trimethylsilyl-containing allylic esters and carbamates, as in the reactions 40->41, and 43->44.The reaction of the silyl-cuprate with allylic esters and the three-step sequence with the allylic carbamates are stereochemically complementary, the former being stereospecifically anti and the latter stereospecifically syn.Homochiral allylsilanes can be ma de by these methods with high levels of stereospecificity, as shown by the synthesis of the allylsilanes 54, 58 and 59.
