(2-((3R,5R)-3,5-Bis((tert-butyldimethylsilyl)oxy)cyclohexylidene)ethyl)diphenylphosphine oxide → (R)-1-[(3R,5R)-3,5-bis-(tert-butyldimethyl-silanyloxy)-cyclohexylidene]-7,11-dimethyl-11-trimethylsilanyloxy-dodec-2-ene

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Reaction Steps

8.55 g of carefully dried (3R,5R)-[2-[3,5-bis-(t-butyldimethyl-silanyloxy)-cyclohexylidene]-ethyl]-diphenyl-phosphine oxide (Tetrahedron Lett. 32, 7663 (1991)) was dissolved in 90 ml of abs. THF and treated at -78° with 10.9 ml of nBuLi (1.6M, hexane). After 20 minutes, 2.27 g of (S)-5,9-dimethyl-9-trimethylsilanyloxy-decanal, dissolved in a small amount of THF, was added dropwise to the deep red solution. The mixture was kept for 0.5 h at -78° and for 4 h at ambient temperature. After quenching with crushed ice/ KH2PO4, the product was extracted twice with ether, washed with water and brine, dried over sodium sulfate and the solvents removed i.V. Flash chromatography (SiO2, hexane/ AcOEt) yielded in the less polar fractions 3.840 g of (R)-1-[(3R,5R)-3,5-bis-(tert-butyldimethyl-silanyloxy)-cyclohexylidene]-7,11-dimethyl-11-trimethylsilanyloxy-dodec-2-ene, as colorless oil, which was deprotected as described in the following paragraph. 2.40 g of phosphine oxide, which had been used in excess, were recovered in the more polar fractions.

Provenance & Evidence