Chemistry of organosilicon compounds. 99. Conjugate addition of allylsilanes to .alpha.,.beta.-enones. A New method of stereoselective introduction of the angular allyl group in fused cyclic .alpha.,.beta.-enones

Lewis Acid-Promoted Cycloaddition Reaction of Cyclopropanes with Allylsilanes.

“…1) In addition, allylsilanes are excellent reagents for the construction of fourand five-membered ring systems because they function as the synthetic equivalent of the silyl-substituted 1,2-and/or 1,3-dipole.…”

Bicyclo[2.2.2]octane analogues of patchouli alcohol by Sakurai reaction and Nagata cyclization. Synthesis and olfactory properties of novel isopropyl derivatives

“…To a stirred solution of 8 (380 mg, 2.3 mmol) in THF (3 mL) NaH (0.8 g, 3.5 mmol) was added portionwise under Ar and the mixture was stirred at r.t. for 40 min. CH 3 I (4 mL, 0.07 mol) was then added dropwise and the mixture refluxed under Ar until TLC monitoring (SiO 2 ; petroleum ether (40-70°)/Et 2 O: 9/1, R f (8)<R f (9)) showed the disappearance of the starting material. The reaction mixture was neutralized with 0.5N HCl, washed with H 2 O, brine, dried with anhydrous Na 2 SO 4 and evaporated at atmospheric pressure.…”

“…A solution of compound 9 in anhydrous THF (10 mL) was treated with LiAlH 4 (130 mg, 3.3 mmol). The reaction mixture was stirred at r.t. until TLC analysis (petroleum ether (40-70°)/Et 2 O: 9/1, R f (10)<R f (9)) showed the disappearance of the starting material (1h). Excess LiAlH 4 was quenched by dropwise addition of H 2 O and neutralized with 0.1N HCl.…”

Synthesis of cedranoid sesquiterpenes. II. Functionalization at carbon 12

“…However, the use of a large variety of reagents and conditions that had previously been used for the conjugate addition of a vinyl group to a,p-unsaturated carbonyl compounds (see Experimental) failed to effect homoconjugate a d d i t i~n .~ Nor could such addition be effected with lithium diisobutylhex-lenylmethylalanate (12) or with the potassium or thallous derivatives of diethyl malonate (9,13). Attempted homoconjugate addition of an allyl group with allytrimethylsilane and titanium tetrachloride (14) led instead to homoconjugate addition of chloride ion to give 9, which showed the typical strong ir bands at 6.06 and 6.21 pm of the enolized P-keto ester system of homoconjugate addition products from 6. We subsequently found that the same product is formed in the presence of titanium tetrachloride alone.…”

“…The failure to add an allyl group indicates that, while the ethylenic bond of allyltrimethylsilane may be relatively nucleophilic (15), chloride ion is a much better nucleophile under the conditions used. It is possible that in the case of conjugate addition to a,P-unsaturated ketones (14), conjugate addition of chloride also occurs, but is reversible. 9 X = CI, E = C02Me l l a R' = (c&I~c=c)~~oH,…”