Selenium stabilized carbanions. Preparation of .alpha.-lithio selenides and applications to the synthesis of olefins by reductive elimination of .beta.-hydroxy selenides and selenoxide syn elimination

Abstract

The deprotonation of several alkyl aryl selenides with lithium amide bases has been studied. The kinetic acidity of methyl m-trifluoromethylphenyl selenide was found to be 1/3.8 that of the sulfur analogue. The introduction of a m-trifluoromethyl substituent into methyl phenyl sulfide increased the kinetic acidity by a factor of 22.4. A variety of /3-hydroxy selenides have been prepared by the reduction of -phenylseleno ketones and the addition of -lithio selenides (prepared by deprotonation of benzyl phenyl selenide, bis(phenylseleno)methane, methoxymethyl m-trifluoromethylphenyl selenide, and phenylselenoacetic acid, and by n-butyllithium cleavage of bis(phenylseleno)methane) to carbonyl compounds. These /3-hydroxy selenides are converted to olefins on treatment with methanesulfonyl chloride and triethylamine. This reductive elimination proceeds exclusively or predominantly with anti stereochemistry. Simple olefins, styrenes, cinnamic acids, vinyl ethers, and vinyl selenides have been prepared using this technique. Attempts to carry out the syn reductive elimination of /3-hydroxy selenox-

Regioselectivity of the Intramolecular Photocycloaddition of α,β-Butenolides to a Terminal Alkene

“…Diisopropylamine was freshly distilled over NaOH. Phenylselenoacetic 34 and 2-phenylselenopropionic 35 To a stirred, cold solution of 5-(but-3-enyl)-3-phenylseleno-2-oxolanone (276 mg, 0.93 mmol) and AcOH (2 drops) in THF (3 mL) was added drop-wise 30% H 2 O 2 (0.80 mL, 7.0 mmol), keeping the temperature below 0 ºC. The mixture was stirred at 0 ºC for 45 min, then neutralized with sat.…”

Benzeneselenenyl Reagents in Organic Synthesis

“…Increased reactivity is observed if diphenyl diselenide (2) is reduced with lithium aluminium hydride in dioxane [36,371. Uncomplexed benzene selenolate (la), which in some cases exhibits higher reactivity, is generated by the reduction of diphenyl diselenide (2) with sodium hydride [38], sodium metal [35, 391, rongalite (sodium formaldehyde sulfoxylate) [40], under phasetransfer conditions (50% NaOH, dichloromethane, triethylbenzylammonium chloride) [41] or electrochemically [42].…”

“…The use of epoxides (50) as electrophiles leads to Phydroxy alkylselenides (51) [8,40,941. Larger cyclic ethers can be cleaved with selenide obtained from the reduction of diphenyl diselenide (2) with lithium aluminium hydride in dioxane (scheme 8).…”

Regio-and Stereoselective Ring Opening of Epoxides with Sodium Phenylselenide under Phase Transfer Conditions

“…8,9 Liotta 10 later introduced the useful variation of reducing the Se-Se bond with Na o in refluxing THF followed by solvation in HMPA. Alternatively reduction of Ph-Se-Se-Ph can be accomplished with Na o and ultrasound in THF, 11 resin bound borohydride, 12 LiAlH 4 , 13 NaH in boiling THF, 14 sodium formaldehyde sulfoxylate, 15 hypophosphorous acid, 16,17 NaBH 4 /AlCl 3 system, 18 tributylphosphine and 10% NaOH, 19 methyllithium 20 in ether or Zn/ZrCl 4 10 system. The deprotonation of PhSeH with NaH in dry refluxing THF has also been reported.…”