Mechanism of hydride reduction of 1-alkyn-3-ols

Abstract

Hydride reduction of l-alkyn-3-ols (3) is shown to proceed via site-specific hydride transfer to C-2. A mechanism is proposed which rationalizes the observed reciprocal relationship between solvent basicity and the extent of cis reduction for these systems.

A regio- and stereoisomeric study of allylic alcohol fluorination with a range of reagents

“…This gave 5a in much higher diastereoisomeric excess (de 62%, determined by chiral GC-FID). The two product mixtures of 5a/5b were then transformed separately by propargylic reduction to the corresponding allylic alcohols 1a/1b using LiAlH 4 [15] as illustrated in Scheme 2. These allylic alcohol reductions gave exclusively the E-olefins.…”

Reversible Charge-Accelerated Oxy-Cope Rearrangements

“…When Red-Al 19 was discovered to be ineffective for performing this interconversion, recourse was made instead to lithium aluminum hydride. 20 In the event, refluxing THF was required, these conditions also cleaving the tert-butyldimethylsilyl protecting group.…”

“…The separated aqueous layer was extracted with CH2Cl2 (×2), the combined organic layers were dried, and the filtrate was evaporated. Chromatography of the residue on silica gel (elution with 4:1 hexanes-ethyl acetate) gave 10 (1.75 g, 90%) as a colorless oil: IR (film, cm -1 ) 3456; 1 H NMR (300 MHz, CDCl3) δ 5.79 (d, J ) 3.8 Hz, 1 H), 4.45 (d, J ) 3.8 Hz, 1 H), 4.14 (m, 1 H), 3.98 (d, J ) 2.5 Hz, 1 H), 3.76-3.70 (m, 1 H), 3.61-3.54 (m, 1 H), 3.44 (br s, 1 H), 1.95-1.80 (m, 2 H), 1.39 (s, 3 H), 1.21 (s, 3 H), 0.81 (s, 9 H), 0.00 (s, 6 H); 13 C NMR (75 MHz, CDCl3) ppm 110.8, 104.2, 85.0, 79.5, 75.3, 59.5, 30.7, 26.5, 25.9, 25.6 (3 C), 17.9, -5.8, -5.9; FAB MS m/z (M + + H) calcd 319.19, obsd 319.20; [R] 20…”

Liquid crystals carrying stereodefined vicinal difluoro- and trifluoro- alkyl motifs

“…Thus propargylic alcohol 10, which is readily prepared from aldehyde 9, formed the starting point of the synthesis. Stereospecific reduction 14 with LiAlH 4 generated allylic alcohol 11 which was epoxidised with mCPBA to give the diastereoisomeric allylic epoxides 12a : 12b (not shown) in a 3 : 1 ratio. In order to retain an efficient synthesis, these diastereoisomers were treated as a mixture until later in the synthesis.…”