Horner-wadsworth-emmons reaction: Use of lithium chloride and an amine for base-sensitive compounds

Stereoselective synthesis of 1-deoxynojirimycin, D-glucono-δ-lactam and D-altrono-δ-lactam from a common chiral intermediate derived from D-mannitol

“…The obtained azido-diol compound 14 was subjected to oxidative cleavage with NaIO4 to achieve the corresponding aldehyde. This obtained aldehyde was almost pure and without column purification it was subjected to HWE olefination with triethyl phosphonoacetate under Masamune-Roush conditions 13 to afford the desired, highly E-selective α,β-unsaturated ethyl ester 10 in 93% yield (E:Z, 98:2 based on 1 H NMR analysis).…”

“…The combined organic layers were washed with water (20 mL), brine (30 mL) and dried over Na2SO4, filtered and concentrated. The residue was chromatographed on silica gel with EtOAc-hexane (1:4) to give pure 1,3-diol 12 (8.55 g, 95%) as colorless oil; Rf = 0.4 (hexanes-EtOAc 74.8, 70.7, 65.6, 64.5, 62.6, 35.8, 34.3, 24.9, 23.9, 23.6 (2R,3R,4R)-2-Azido-4,5-(cyclohexylidenedioxy)-1,3-(bisbenzyloxy)pentane (13). To a well stirred solution of NaH (60% dispersion in mineral oil, 3.73 g, 93 mmol) in dry THF (100 mL) under nitrogen was added azido diol 12(8 g, 31 mmol) dissolved in THF (40 mL) via syringe very slowly at 0 o C and allowed to stir at same temperature for 20 min.…”

One-Pot Multi-Reaction Processes: Synthesis of Natural Products and Drug-Like Scaffolds

“…22 The high yields from this one-pot two-step process arose from a combination of not having to isolate the volatile aldehyde intermediates and the mild Masamune-Roush conditions for the HWE reaction. 23 Although other organophosphorus alkene-forming reactions were investigated for the synthesis of the α,β-unsaturated esters, only the HWE reaction consistently gave the E-isomers as the sole products. Reduction of the esters by using 2.2 equivalents of DIBAL-H gave the (E)-allylic alcohols in high yields (81-100%).…”

Model Studies on the Synthesis of Madangamine Alkaloids. Assembly of the Macrocyclic Rings

“…However, disappointingly, all attempts to induce the same stereoselectivity from ketones 14a and 14b, either under the original 12 or slightly modified 13 reaction conditions, resulted in the generation of Z/E mixtures of alkenes 15, in which the undesired E-isomer was predominant (35:65 ratio).…”