Dioxolanyl

An alternative strategy is to put a 3-(-2-dioxolanyl)ethanoyl substituent in place first and then add the C7-substituent by a Grignard addition. This approach was applied to the synthesis of 8.2C but in this case it was found necessary to remove the tosyl protecting group prior to cyclization[l]. 

Mesityl Oxide. Mesityl oxide (MSO) (4-metliyl-3-penten-2-one) is an oily colorless liquid with an unpleasant odor. It exhibits the versatiUty and unusual reactivity associated with conjugated a,P unsaturated carbonyl compounds (172). On standing ia air, mesityl oxide slowly forms bis(3,5,5-trimethyl-l,2-dioxolanyl)-3-peroxide (173). 

Methoxyethoxymethyl, 365 Enamino Derivatives, 365 4-Methyl-1,3-dioxolanyl Enol Acetate, 365 Pyrrolidinyl Enamine, 365 Benzyl Enol Ether, 366 Butylthio Enol Ether, 366 Protection of Tetronic Acids, 366 Trimethylsilyl Enol Ether, 367... 

By application of the Corey-Winter reaction,vicinal diols 1 can be converted into olefins 3. The key step is the cleavage of cyclic thionocarbonates 2 (1,3-dioxolanyl-2-thiones) upon treatment with trivalent phosphorus compounds. The required cyclic thionocarbonate 2 can be prepared from a 1,2-diol 1 and thio-phosgene 4 in the presence of 4-dimethylaminopyridine (DMtVP) ... 

Dioxolanyl oxygens are also effective directing groups.183... 

The diastereoselective ultrasonically induced zinc-copper 1,4-addition of alkyl iodides to chiral a, (i-unsaturaied systems in aqueous media was studied by Suares and co-workers the Z-isomer gives good diastereos-electivities while reactions with the E-isomer are nonstereoselective.63 The 1,4-addition to chiral y, a-dioxolanyl-a, (i-unsaturated esters also proceeds with good yields (51-99%) (Eq.10.29).64... 

The introduction of four 2,2-dimethyl- 1,3-dioxolanyl groups into 18-crown-6 to form compound [245] causes the log K value to drop from 6.48 to below 1.7 (Laidler and Stoddart, 1976). Replacement of two CH2OCH2 units... 

In addition, 2-substituted chiral succinic acid derivatives can be obtained via diastereoselective radical addition of 2-dioxolanyl radicals to ftimaric acid diamides with a de up to 98% (Scheme 19) [25],... 

A novel masked S-formylation of electron-deficient olefins with 1,3-dioxolane in the presence of (n-Bu4N)2S20g has been observed. Thus when cyclic a,-unsaturated ketones, esters and sulfonyl alkenes react with (n-Bu4N)2S20g in 1,3-dioxolane, the corresponding 1,3-dioxolanyl adducts are obtained in excellent yields (equation 28). 

A radical cyclization has been achieved from a 1,3-dioxolanyl-thiocarbonate containing an alkyne group in an appropriate position (Equation 49) <2003TA2961>. The stereocontrol between cis- and trans-ivscd tricycles was 1.5-4.2 1. The products were similar to those depicted in Equation (36). 

Reactions of 1,4-dimethoxynaphthalene and its 2-chloro, 2-bromo, and 2-(1,3-dioxolanyl) derivatives with BAIB/TMSX (X = C1, Br) combinations in dichloromethane result in acetoxylation, monohalogenation, or dihalogenation of the more activated ring (Scheme 26) [79]. Specific outcomes depend on the naphthalene derivative and reaction conditions. It is interesting that the 2-(1,3-dioxolanyl) derivative undergoes ipso-bromination with BAIB/TMSBr, and that this mode of reactivity was not observed with 2-(l,3-dioxolanyl)-l,4-di-methoxybenzene. These reactions are mechanistically diverse. Evidence was presented that bromination occurs after the formation of molecular bromine, and that chlorination probably follows a radical pathway involving the homo-... 

The bis(dioxolanyl)oxazolidinone 33 has been prepared from D-mannitol and evaluated as a chiral auxiliary <02MT749> and the diamine 34 has been examined as a ligand for rhodium catalysed asymmetric hydrogenation of diethyl itaconate <02JOU104>. Deracemisation of 2-benzylcyclohexanone by formation of an inclusion complex with the TADDOL compound 35 has been described and the mechanism clarified by X-ray structure determination of the complex <02T3401>. A production process for the bis(phosphine oxide) 36 has been patented <02USP6472539>. 

The diastereoselectivity for the reaction of 157, which possesses a 2-methyl-1,3-dioxolanyl group, with enolates generated from fert-butyl acetate was found to be highly dependent on the reaction conditions.89 For example, the lithium enolate gave (Ss,S)-158 (72% de) while the titanium enolate afforded (Ss,/ )-158 (92% de). A non-chelation-controlled transition state was used to explain the preferential formation of (Ss,S)-158 while a six-membered chairlike transition state containing a four-membered metallocycle and/or a seven-membered counterpart was proposed for the formation of the (Ss,R)-158. Treatment of (Ss,S)-158 with TFA gave P-amino acid 159 in 70% yield. 

In the presence of mineral acids, the OH groups of 28 can also be replaced by with hydrogen peroxide.27... 

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