Synthesis of optically active (E)-1-alkoxymethoxybut-2-enyl(tributyl)stannanes: stereochemistry of their thermal reactions with aldehydes

Abstract

Menthyloxymethoxy] -(E)-but-2-enyl(tributyl)stannanes (8) and (9), whose configurations were assigned by correlation with ( 2 R )and (2S)-pentan-2-01 (14) and (15), react stereoselectively on heating with benzaldehyde to give (3S,4S)and (3R,4R) -4hydroxy-3methyl-(Z) -1,2-enol ethers (I 6) and (1 8), respectively, the configurations of these products being -i-Prt.

Synthesis of enantiomeric menthol derivatives for forming and probing chiral surfaces. X-ray crystal and molecular structures of (+)-(1S,2R,5S)-1-(2-tricyanovinyl-1H-pyrrol-1-yl-methoxy)-2-isopropyl-5-methylcyclohexane

“…Tricyanovinylpyrrole (C 9 H 4 N 4 , TCVP) was prepared from TCNE and pyrrole in acetone, following the procedure reported in the literature 11 The (1S,2R,5S)-and (1R,2S,5R)-1-(chloromethoxy)-2-isopropyl-5-methylcyclohexane, or (+)-and (À)-chloromethyl-menthyl-ether, enantiomers were prepared from commercial (+)-and (À)-menthol, respectively, according to a recipe reported in the literature. 16 …”

“…The first yellow eluted fraction was collected and evaporated to dryness. After crystallization from n-heptane, light orange crystals of 1 (0.175 g, 38%) were obtained, mp: 83-85°C (Found: C, 71.37; H, 7.42; N, 16 This ester (C 21 H 36 O 2 ) was prepared from menthol and 10-undecynoic acid in CH 3 CN and in the presence of DMAP, Et 3 N, Me 3 NAEHCl and Me 2 NSO 2 Cl according to a procedure reported in the literature for the esterification of menthol. 10 This was purified by column chromatography on silica gel (220-440 mesh) eluting with n-hexane/ethylacetate …”

Stereoselectivity of Chiral Homoenolate Equivalents

“…This preference generally controls the facial selectivity in reactions of enantiomerically enriched 1-substituted but-2-enylstannanes with aldehydes. 57 The epimeric mixture of (1R)-and its methoxymethyl (MOM) ether. 59 Cyclization with BF 3 -Et 2 O at Ð78¡C yielded a 80:4:8:8 mixture of the syn-(Z)alcohol 97 and its diastereomers with anti-(Z)-, syn-(E)-, and anti-(E)-configuration, respectively.…”

Preparation of α-substituted γ-alkoxyallylstannanes from β-tributylstannyl acrolein acetals: scope of the method and primary rationalization of the obtained results

“…Accordingly, the synthesis of a-alkoxyallylstannanes previously described in achiral series [25][26][27] became of crucial interest when enantioenriched chiral a-oxygenated species were involved. The pioneering preparation based on separation of diastereomeric mixtures of a-(menthyloxymethyl)crotyltributylstannanes [28,29] has been rapidly replaced by enantioselective preparations.…”