Relative reactivities of cycloalkanone dimethyl ketals to hydrogenolysis by dichloroaluminum hydride

Abstract

The relative rates of hydrogenolysis of a series of cycloalkanone dimethyl ketals by AlClaH to the corresponding cycloalkyl methyl ethers have been determined. The order of reactivity varies with ring size in the following manner:

Stripping off Water at Ambient Temperature: Direct Atom-Efficient Acetal Formation between Aldehydes and Diols Catalyzed by Water-Tolerant and Recoverable Vanadyl Triflate

“…Conventionally, acetal formation at ambient temperature requires the use of 1,1-dimethoxyacetals as aldehyde precursors or orthoformates (HC(OR) 3 ) as dehydrating agents with concomitant generation of formate ester and release of ROH. Normally, the catalysts employed include HCl, p -TSA/TFA, Amberlyst-15, BF 3 ·Et 2 O, metal halides (e.g., TiCl 4 , ZrCl 4 , LaCl 3 , WCl 6 , 9a, FeCl 3 , and DCC/SnCl 4 ), metal triflates (e.g., TMSOTf, Sc(NTf 2 ) 3 , and Bi(OTf) 3 ), and N -bromosuccinimide (NBS) . Many of these are acidic in nature.…”

Synthesis of some brominated cage molecules as possible precursors to pentaprismane

“…Finally, elution with methylene chloride gave the crude adduct 5 as a red oil (4.0 g), which crystallized on standing at room temperature to give yellowish needles (3.43 g, 30% from 1): mp 115-116 °C (lit. 112-113.5 °C (2)); IR (KBr) 1675 (s), 1615 (m) cm"1; NMR (CDCI3 + acetone-de) 6.63 (s, 2 ), 6.00 (d, Jc* 2 Hz, 2 H), 3.5-3.6 (m, 3 ), 3.50 (s, 3 H, OCH3, overlap with the m), 3.33 (s, 3 H, OCH3).…”

“…The solution was then decolorized with charcoal, filtered, and evaporated in vacuo to give a dense yellow oil (0.845 g). This crystallized from ethyl ether as tiny colorless needles (0.66 g, 70%): mp 134-135.5 °C; NMR (CDCI3) 3.63 (s, 3 H, OCH3), 3.60 (s, 3 H, OCH3), 2.80-3.60 (complex m, 7 H); IR (KBr) 1770 (s), 1755 (s); mass spectrum, m/e (relative intensity) 312 (23.9), 314 (23.7) (molecular ion), 233 (32), 206 (14), 205 (97), 201 (6), 131 (60), 128 (64), 119 (100), 117 (90), 103 (48), 77 (67), 59 (50), 51 (62). 3 -Bromo -1,7-dlchloro-4,4 -dlmethoxypentacyclo -[5.4.0.026.O310.Os'9]undecane-8,11 -dlone (9).…”

Reduction of quarternary ammonium salts with lithium triethylborohydride. Convenient method for the demethylation of substituted trimethylammonium salts

“…Trans-Crotonaldehyde diethyl acetal9 5 was prepared from frans-cortonaldehyde and triethyl orthoformate by a method previously described. 6 trans-Crotyl ethyl ether10 4 was prepared by the dichloralane hydrogenolysis of irans-crotonaldehyde diethyl acetal by a method previously described. 5 Competitive hydrogenolyses of 1 and 5 with alane were carried out according to the procedure of Davis and Brown.5 Reaction of 2-Butynal Diethyl Acetal 1 with LiAlH4.…”