95674-80-9Relevant articles and documents
Chiral Synthesis via Organoboranes. 35. Simple Procedures for the Efficient Recycling of the Terpenyl Chiral Auxiliaries and Convenient Isolation of the Homoallylic Alcohols in Asymmetric Allyl- and Crotylboration of Aldehydes
Brown, Herbert C.,Racherla, Uday S.,Liao, Y.,Khanna, Vijay V.
, p. 6608 - 6614 (1992)
Asymmetric allyl- and crotylboration of aldehydes, RCHO, with terpenyl-based allyl- and crotylborane reagents Ter2*BAll (1), Ter2*BCrtZ (2), and Ter2*BCrtE (3, Ter* = Ipc, 4-Icr and 2-Icr; All = allyl and Crt = crotyl), afford Ter2*BOCH*(R)C*(1R)(2R)CH=CH2 intermediates 4.In these reactions, the isolation of homoallylic alcohols, HOCH*(R)C*(1R)(2R)CH=CH2 (5), can be accomplished via oxidation of 4 with alkaline hydrogen peroxide.Unfortunately, oxidative workup destroys the chiral auxiliary and produces a large amount of nonrecyclable byproduct, terpenol (Ter*OH).Further, isolation of the pure homoallylic alcohol by distillation can be difficult if it boils in the range of the abundant byproduct.Therefore, in order to recycle the chiral auxiliaries and isolate the product homoallylic alcohols in an efficient manner, we have developed the following procedures: (1) elimination workup, in which enantiomerically pure α-pinene and Δ2- and Δ3-carenes are liberated from terpenylborinates 4 by treatment with isobutyraldehyde and 1 mol percent BF3*OEt2; (2) ethanolamine workup involving treatment of 4 with ethanolamine (EA) to achieve the precipitation of the ethanolamine adducts (EA-BTer2*, Ter* = Ipc and 2-Icr, 11 and 12) from which the Ter2*BOMe can be easily regenerated; and (3) 8-hydroxyquinoline workup, involving treatment of 4 with 8-hydroxyquinoline (8-HQ) to precipitate the 8-HQ adducts (8-HQ-BTer2*, Ter* = Ipc, 4-Icr and 2-Icr, 13-15), from which the various Ter2*BOMe intermediates can be conveniently liberated.It is hoped that these procedures will significantly enhance the scope of asymmetric allyl-/crotylboration of aldehydes with Ter2*BAll (1), Ter2*BCrtZ (2), and Ter2*BCrtE (3) and serve as excellent alternatives for any catalytic versions yet to be discovered.
Hydrated ?-bonded organometallic cations in organic synthesis. I. Allyl-, crotyl-, 1-methylallyl-, cyclohex-2-enyl-, and cinnamyl-stannation of carbonyl compounds in water
Furlani, Donatella,Marton, Daniele,Tagliavini, Giuseppe,Zordan, Michele
, p. 345 - 356 (2007/10/02)
Homoallylic alcohols can be prepared in water by allyl-, crotyl-, 1-methylallyl-, cyclohex-2-enyl-, or cinnamyl-stannation of such carbonyl compounds as aldehydes, dialdehydes, and ketones, as well as acetals.The procedure is based on: Bu2RSnCl + R'COR" + (1/2)H2O -> R(HO)CR'R" + (1/2)(Bu2SnCl)2O where R = allyl, crotyl, 1-methylallyl, cyclohex-2-enyl, or cinnamyl group, R' = H or alkyl group, R" R'= alkyl group.In most cases, the reaction products are obtained rapidly in high yields (80-100percent).Hydrated organometallic cations Bu2RSn+(aq) are partly involved.These results, together with those already published on 2-propynyl-and allenyl-stannation, indicate the value of this procedure.
Stereochemical Aspects of Aldehyde Additions to Cyclohex-2-enylstannanes
Young, David,Kitching, William
, p. 1767 - 1777 (2007/10/02)
Cyclohex-2-enylation of aldehydes, mediated with boron trifluoride etherate, involves γ-equatorial approach of the presumed aldehyde-Lewis acid adduct (RCHO-BF3), irrespective of starting stannane stereochemistry.Marginal threo selectivity characterizes homoallyl alcohol formation from benzaldehyde, whereas alkanals react with high erythro selectivity, so that 1-(1'-hydroxyalkyl)cyclohex-2-enes in this diastereomeric form are available based on allyltin chemistry.
