Acetals dialkyl

Acrolein at a concentration of <500 ppm is also used to protect Hquid fuels against microorganisms. The dialkyl acetals of acrolein are also useful in this apphcation. In addition, the growth of algae, aquatic weeds, and moUusks in recirculating process water systems is also controlled by acrolein. 

Methods similar to those used to form and cleave dimethyl acetal and ketal derivatives can be used for other dialkyl acetals and ketals. 

From a dialkyl acetal Bu3SnSPh, Bp3 Et20, toluene, —78° -> 0°, 64-100% yield. These conditions also convert MOM and MEM groups to the corresponding phenylthiomethyl groups in 64-77 % yield. 

From a dialkyl acetal MgBr2, Et20, it, PhSH, 91% yield. MOM groups are converted to phenylthiomethyl groups, 75% yield. 

Erom a dialkyl acetal Bu3SnSPh, BF3-Et20, toluene, —78° 0°, 64-100%... 

Monoalkylated and dialkylated acetic acids can be prepared by the malonic ester synthesis, but trialkylated acetic acids (R3CCO2H) can t be prepared. Explain. 

Derivatization (GC) 848 alkylating reagents 861 alkyl halide/catalyst 861 dialkyl acetals 863 diazoalkanes 862 extractive alkylation 863 pyrolytic alkylation 865 al) ldimethylsilyl reagents 855... 

A new class of functional comonomers exemplified by acrylamidobutyraldehyde dialkyl acetals 1 and their Interconvertible cyclic hemlamidal derivatives 2 were prepared and their chemistry was Investigated for use In polymers requiring post-crosslInking capability. These monomers do not possess volatile or extractable aldehyde components and exhibit additional crosslinking modes not found with conventional am1de/forma1dehyde condensates, eg, loss of ROH to form enamides 9 or TO and facile thermodynamically favored reaction with diols to form cyclic acetals. 

The most convenient synthetic approach to compound 1, acrylamidobutyraldehyde dialkyl acetal (ADDA), Is shown In Scheme 2. 

Acrylamidobutyraldehyde dialkyl acetal (1, ABDA, R=Me, Et) and N-acryloyl-2-ethoxypyrrol1d1ne (2, AEP) were synthesized as described In the previous paper (1) and used directly. 

Bicyclopropylidene (1) reacts with dimethoxycarbene generated thermally from the diazirine at 25 °C to give a complex mixture of products [116b]. The cycloaddition of several dialkoxycarbenes generated in situ from the corresponding 2,2-dialkoxy-A -l,3,4-oxadiazolines of type 134 with bicyclopropylidene (1) affords the dialkyl acetals of dispiro[2.0.2. l]heptanone 135 (Scheme 29 ) [1251. 

The attempted transacetalization of the dimethyl acetal 135 a was partially successful only when it was boiled in excess ethanol in the presence of boron trifluoride etherate. The formation of the corresponding diethyl acetal 137 indicates that dialkyl acetals of dispiro [2.0.2. l]heptan-7-one can, in principle, enter reactions without ring opening and thus be applied as a synthetic equivalent of [3]triangulanone (Scheme 30) [125]. 

Several further publications report on the (—)-sparteine-mediated addition of alkyl-or aryllithium onto imines or the C=N bond of isoquinolines . Usually, the achieved enantiomeric excesses are low and, sometimes, other chiral ligands serve better. As reported by Muller and coworkers, the nucleophilic substitution of arenecarbaldehyde dialkyl acetals by o-substituted aryllithium reagents is an alternative . 

A facile acid-catalyzed double cyclization of A,A-dibenzylaminoacetaldehyde dialkyl acetals of type 125 has been known to generate l-azadibenzo[c,/]bicy-clo[3.3.1]nona[3,6]dienes 126 in high yields 120,121,147). A novel and convenient synthesis of ( )-amurensinine (25) and ( )-reframine (28) (Scheme 25) proceeds from the quaternary salt 127, where proper choice of base and reaction... 

The acid-catalyzed cyclization of properly substituted aminoacetaldehyde dialkyl acetals was shown to be a suitable method in the construction of a homo-isopavine (Scheme 39) (132a,172). Treatment of 7V-[l,3-bis(3,4-dimethoxy-phenyl)propyl]aminoacetaldehyde dimethyl acetal (175) with concentrated hydrochloric acid afforded the 7V-norhomoisopavine 176 in 39% yield. This cyclization was also accompanied by some O-demethylation. Product 176 could be readily N-methylated using formaldehyde and sodium borohydride to afford the homoisopavine ( )-177 (772). 

It is important to note that a possible photochemical ring expansion by [1,3]- or [l,5]-acyl shifts in the 5-membered vinyl lactams 191 has not been observed,4,116 nor have [l,5]-shifts of acyl groups involving an aromatic ring been reported for either enol esters or enamides. However, an example of a similar [l,5]-alkyl shift, 193 -> 194, in related ketene dialkyl acetals is known.24... 

Other industrial processes are the liquid-phase oxidation in the presence of cobalt catalysts [171] and the electrochemical oxidation in the presence of lower aliphatic alcohols via the corresponding anisaldehyde dialkyl acetal [172]. 

Cyclization of aryIthioacetaldehyde dialkyl acetals and arylthiomethyl ketones 877... 

CH3SH and C2H5N[CH(CH3)2]2 (equation I). Under the same conditions dialkyl acetals can be converted into 0,S-acetals (equation II). MEM and MOM ethers can be converted into cyanomethyl ethers (ROCH2CN) by sequential reaction with (CH3)2BBr and Bu4NCN in 80-90% yield. 

Preparation.l Dialkyl acetals of DMF are generally prepared by transacetal-ization of the dimethyl or diethyl acetal, but this reaction is not useful in the case of the di-r-butyl acetal. Replacement of one methoxy group of DMF dimethyl acetal occurs on refluxing in f-butyl alcohol conversion to the dw-butyl acetal is effected in the presence of 2,4,6-tri-f-butylphenol (equation I). 

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