A new vinylsilane substitution reaction with glyoxylate: asymmetric synthesis of .alpha.-hydroxy .beta.,.gamma.-unsaturated esters

Abstract

Representative experimental procedures and copies of 13C and 1H NMR spectra and mass spectra of all new products (71 pages). Ordering information is given on any current masthead page.(15) Reduction of 11a with BugSnD (25 °C) gave an 88/12 ratio of anti/syn deuteration, while reduction of lib gave a 23/77 ratio. Deuteration ratios were determined by NMR, and proton assignments were made by the standard trends Jmt¡ > J^( see ref 14).(16) (a) Related allylations of (3-alkoxy esters have just recently appeared.

Stereochemical Control in Organic Synthesis Using Silicon-Containing Compounds

“…Otherwise, stereocontrolled reactions of vinylsilanes with carbon electrophiles have mostly been used in synthesis in intramolecular versions, although a few intermolecular reactions have been carried out and are known to take place with retention of configuration, , as in the synthesis of nuciferal 118 (Scheme ) 26 …”

Catalytic Asymmetric Prins Bicyclization for the endo‐Selective Formation of 2,6‐dioxabicyclo[2.2.2]octanes

“…This may be regarded as the rate‐determining step, as in the case of R 1 ≠R 2 rotation of the carbenium ion sigma bond in III leads to some loss of diastereoselectivity at position 5 of the product 7 n (Table ). Alternatively, analogous to Mikami's glyoxylate‐initiated Prins cyclization, the double bond of 6 could nucleophilically add to complex 2′ or 10′ without any pre‐coordination of the substrate carbonyl groups (path B). However, as previously demonstrated in asymmetric Prins cyclizations, the facial selectivity of the aldehyde is well under control of a chiral acid (A in 10′ ), whereas the diastereofacial selectivity of the double bond is not.…”

Catalytic Enantioselective Arylation of Glyoxylate with Arylsilanes: Practical Synthesis of Optically Active Mandelic Acid Derivatives

“…We have already reported chiral dicationic Pd complex‐catalyzed highly enantioselective alkenyl‐, dienyl‐, and trienylation employing the corresponding silyl compounds as nucleophiles 12. 13 As an initial experiment under a similar condition, the treatment of ethyl glyoxylate 2 with arylsilane 1a in the presence of 5 mol % of various chiral dicationic Pd complexes, which are generated in situ by adding slight excess of AgSbF 6 (2.2 equiv) to the corresponding neutral dichloro Pd complexes,10b, 12 in dichloromethane at room temperature for 24 h afforded the desired adduct 3a after the desilylation with 1 n HCl/THF solution (Table 1). The effect of chiral diphosphine ligands was critical in this reaction.…”