Acetal dimethylacetamide dimethyl

Hydroxyalkyl)porphyrins,84-85 I07b 109 easily accessible from porphyrins by Friedel-Crafts acylation and subsequent reduction, undergo a stereoselective Claisen rearrangement with N,N-dimethylacetamide dimethyl acetal. The substitution pattern and the stereochemical arrangement of the derived chlorins match those of naturally occurring chlorins9 (see Section 1.2.1.2.). 

A. Claisen Rerrangements of Ketene Aminats and Imidates. A reaction that is related to the orthoester Claisen rearrangement utilizes an amide acetal, such as dimethylacetamide dimethyl acetal, in the exchange reaction with allylic alcohols.257 The products are y, 8-unsaturated amides. The stereochemistry of the reaction is analogous to the other variants of the Claisen rearrangement.258... 

The intermediate acylamidine 244 functions as the three-atom component in reaction with hydroxylamine to give the [l,2,4-oxadiazol-5-yl]pyrazole 245, where the intermediate acylamidine 244 was obtained in good yield from reaction of the corresponding amide 243 with dimethylacetamide-dimethyl acetal (Scheme 37) <1999JME2218>. 

The reaction of /V,/V-dimethylacetamide dimethyl acetal and dimethyl malonate at ambient temperature for 1 week, and that of l-benzyl-2-pyrrolidone dimethyl acetal and dimethyl malonate in boiling methanol for 36 hr, gave N, N-disubstituted aminomethylenemalonates (332) in 60% and 87% yields, respectively (69JA6683). 

A straightforward synthesis (Scheme 3) of a furocoumarin-thymidine furan-side adduct was developed <1997JOC2630>. The methoxymethyl (MOM)-protecting group in 33 was removed in 91% yield with ethanolic HCl, and the resulting phenol 34 was condensed with dimethylacetamide dimethyl acetal in the presence of 4 A... 

To a solution of the allylic alcohol 150 (16.7 g, 49.7 mmol) [Eq. (28)] in 500 mL of toluene, under argon, was added AfAf-dimethylacetamide dimethyl acetal (33.117 g, 249 mmol). The reaction mixture was heated at reflux for 10 h, with continuous removal of methanol by molecular sieve (4 A) trap. The reaction mixture was then cooled to room temperature and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel (EtOAc) to afford compound 151 (13.6 g, 68%) as a white foam. The corresponding acetate was obtained in 27% yield and quantitatively transformed into 151 a]D +2.7° (c 1.1, CHClj). 

Dimethylanisole A,A-Dimethylacetamide A,A-Dimethylaniline A,A-Dimethylacetoacetamide (See DMA, dimethylacetamide) dimethyl acetylenedicarboxylate A,A-Dimethylacetamide diethyl acetal 2-Dimethylaminoethyl methacrylate Dimethylaminopropylamine... 

Meerwein describes the preparation of N,N-dimcthylacetamide diethyl acetal. Reaction with vicinalcis-dioh. N,N-Dimethylacetamide dimethyl acetal (2) reacts with vicinal cis-diols such as methyl jS-D-ribofuranosidc (I) in 1,1,1-trichloroethane to give the acetal (.3) in over 80% yield. This derivative is stable under anhydrous... 

Reaction with aUyhc alcohols (1, 271 272). The reaction of rran.v-3-penten-2-ol (1) with N, N-dimethylacetamide dimethyl acetal and/or its synthetic equivalent 1 -methoxy-l-dimcthylaminoethylene in refluxing xylene for 17 hr. gives the N,N-dimethylamide of 3-mcthyl-4-trani-hexenoic acid (2) in 80% yield. When the reaction was carried out... 

C6H15N02 N,N-dimethylacetamide dimethyl acetal 18871-66-4 391 15 33.532 1,2 9363 C6Hl80Si2 bistrimethyl silyl oxide 107-46-0 373.67 31.892 2... 

The reaction outlined in O Scheme 59 is an example of a variant of the Claisen rearrangement of allyl ketene aminal (so-called Eschenmoser-Claisen rearrangement) [87], The reaction dose not require an acid catalyst glycal was just heated with dimethylacetamide dimethyl acetal to form ketene aminal, which underwent the sigmatropic rearrangement to form the corresponding )/,5-unsaturated amide. 

Related to the orrAo-ester rearrangement is the Eschenmoser variation, which involves exchange of A, A -dimethylacetamide dimethyl acetal with an allylic alcohol and in situ rearrangement of the intermediate ketene 0-acetal to furnish the corresponding unsaturated amides. Again, transfer of stereochemistry from the allylic alcohol to the product is observed. ... 

The first total synthesis of (+)-stenine has been accomplished in the laboratory of D.J. Hart/ The key steps were an intramolecular DIels-Alder reaction, an amidine variant of the Curtius rearrangement, an Eschenmoser-Clalsen rearrangement, a halolactonization, and a Keck allylation. The allylic alcohol precursor and A/,A/-dimethylacetamide dimethyl acetal was heated to reflux in xylenes for 4h to afford the desired amide in 93% isolated yield. The transition state most likely adopted a boatlike conformation. 

During the asymmetric total synthesis of (+)-pravastatin by A.R. Daniewski et al., one of the stereocenters was introduced with the Eschenmoser-Claisen rearrangement. The tertiary alcohol intermediate was heated in neat N,N-dimethylacetamide dimethyl acetal at 130 °C for 48h, during which time the by-product methanol was distilled out of the reaction mixture to afford the desired amide in 92% yield. 

AMIDE-CLAISEN REARRANGEMENT N,N-Dimethylacetamide dimethyl acetal. 

Chloroprene Delrin 500F Texin 480AR Lead Chloride Sodium Thioarsenate Sodium Thioarsenate Sodium Thioarsenate Dowfax 2A1 Silicate Aroclor 5442 Lead Bromide Potassium Perborate Aroclor 1248 Potassium Borate Sodium Chromate Potassium Acetate Sodium Acetate Pyruvic Acid Perchloroethylene Perclene Tetrach loroethylene Dimethylacetamide Dimethyl Acetamide (N.N-) Methyl Abietate Aktivin... 

A synthesis of ( + )-dihydrocorynantheol and its C(3)-epimer incorporates a very neat step to introduce the C(15)-substituent. The allyl alcohol (56), easily synthesised via Ban s procedure, was treated with NN-dimethylacetamide dimethyl acetal giving (58), presumably by way of the species (57) and a Claisen rearrangement. 

The acetimidamide side chain originating from the reaction of the amino group in 3-aminopy-ridazine-4-carbonitrile with A.A-dimethylacetamide dimethyl acetal (vide infra) has been used for pyridine ring closure. Thus, treatment of 3- [(l-dimethylamino)ethylidene]amino pyrid-azine-4-carbonitrilc with lithium diisopropylamide at — 70°C gives 7V, (V7-dimethylpyrido-[2,3-c]pyridazine-5,7-diamine (10).21... 

A mixture of A W-dimethylacetamide dimethyl acetal (1.33 g, 10 mmol) and the anhyd cyclic amine (20 mmol) was heated to 190 rC for 5 h, a slow stream of dry N2 being bubbled through the solution. After cooling, 4-benzoyl-6-chloropyridazin-3-amine (234 mg, 1 mmol) was added. The mixture was heated to 120 "C for 30 min, then it was evaporated in vacuo. The products were purified by column chromatography and recrystallized (EtOAc). 

As there are difficulties in exchanging the 2-ethoxy group for an amino substituent, the condensation of a 5-aroylpyridazin-4-amine with A,)V-dimethylacetamide dimethyl acetal provides a better route to 4-aryl-iV,Ar-dimethylpyrido[2,3-d]pyridazin-2-amine 5a.66 If, in the reaction with 5-benzoylpyridazin-4-amine, A, A dimethylacetamide dimethyl acetal is used together with cyclic secondary amines, the corresponding 4-phcnylpyrido[2.3-r/]pyridazin-2-amines 5b g are obtained.67... 

---