2,2-dimethylpropanoyl

To a suspension of AICI3 (89 g, 0.67 mol) in 1,2-dichloroethane (600 ml) chloroacctyl chloride (56ml, 0.70mol) was added dropwise at 0°C. After the addition was complete the mixture was kept at ambient temperature for 15 min, at which lime l-(2,2-dimethylpropanoyl)indole (30 g, 0.15 mol) was added over 3 h. After completion of the addition, the mixture was stirred for 15 min and then poured into ice-cold water. The mixture was extracted with 1,2-dichloroethane. The extract was washed with water (3 x) and aq. 5% NaHCOj (3 X), dried (Na2S04) and concentrated in vacuo. The residue was... 

Dimethylpropanoyl)-l, 2,3,4-tetrahydroisoquinolincs 16 form dipole-stabilized lithium carbanions on deprotonation, but their addition to aldehydes or methyl ketones proceeds nevertheless with low simple diastereoselectivity22 23. However, a high preference for the formation of the w-diastereomer is observed after transmetalation with magnesium bromide22"24. 

Dimethylpropanoyl)-l,2,3,4-tetrahydro-l-(l-hydroxyalkyl)isoquiiiolines (18) General Procedure24 ... 

It is particularly appealing that the configuration at the a-carbon atom in the w-diastereo-mers m-18 can be inverted by trifluoroacetylation and migration of the 2,2-dimethylpropanoyl group24. Furthermore, A-deprotection is possible through simple operations24. 

Less extended investigations have been carried out for the stereochemistry of further substitution reactions, which mostly proceed with lower regioselectivities a-carboxylation (inversion) reaction with methyl chloroformate in the a-position (inversion) a-acylation by 2,2-dimethylpropanoyl chloride (inversion)" y-methylation by methyl iodide (anti-S g) and methyl triflate syn-S f° , intramolecular reactions with allyl chlorides (a, inversion or y, awh -S see Section IV.C.3). 

Methylpropanoyl fluoride gives88 a very low yield of the a-fluoro derivative on fluorination with potassium tetrafluorocobaltate(III) at 250 C, while 2,2-dimethylpropanoyl fluoride gives no carbonyl-containing products. 

Alkylcarbonyl nitrenes have only rarely been used for intermolecular cycloaddition reactions. 2,2-Dimethylpropanoyl nitrene reacts in the usual manner with cyclohexene giving the aziridine (45%) as well as the... 

The use of carbon dioxide as the mobile phase also means that it is possible to carry out assays considerably below subambient temperatures. At -50°C, Gasparrini et al. used a DACH-DNB column to resolve the enantiomers of the thermally enantiolabile 2-methyl-l-(2,2-dimethylpropanoyl) naphthalene, which can undergo rotation around the CO-CAr bond [54]. Reducing the temperature resulted in negligible degradation in column performance. 

DIMETHYLPROPANOYL CHLORIDE see DTS400 DIMETHYL PROPIOLACTONE see DTHOOO... 

SCHEME 12. The 3-acetoxy-2,2-dimethylpropanoyl protecting group internally quenches the C-like dioxolenium ion to lead to a highly delocalized E-like ion. This prevents acyl transfer and promotes stereoselectivity. 

Reaction of l,2,3-tri-ter/-butyl-3,4-dichlorocyclobutene with aqueous base (i.e. sodium hydrogen carbonate) gives l,2-di-/cr/-butyl-3-(2,2-dimethylpropanoyl)cyclopropene (17) in nearly quantitative yield, most probably also proceeding via a 4-chlorocyclobut-2-en-l-ol. ... 

Many other acetamidopteridines have been made in a similar fashion. Other acylation reactions which have been used commonly are trifluoroacetylation, benzoylation, and reaction to form (2,2-dimethylpropanoyl)amidopteridines. 

The introduction of the 2,2-dimethylpropanoyl group into pteridines is a valuable reaction as it greatly increases the solubility of pteridines in organic solvents and it can be easily removed. Thus other reactions of pteridines can be more readily carried out. This reaction is exemplified by the preparation of 6,7-dimethyl-2-[(2,2-dimethylpropanoyl)amino]pteridin-4(3//)-one (3)265 which illustrates the general method. 

Dimethyl-2- (2,2-dimethylpropanoyl)amino pteri(lin-4(3//)-[Pg.304]

This reaction is exemplified by the synthesis of 6,7-diphenyl-2-(2,2-dimethylpropanoyl)-pteridin-4-amine (8).265 The reaction also occurs when R = Me R2 = H, however, the reaction fails when R1 = R2 = Me due to the acidity of the 7-methyl group. 

Coupling of Acetylenes with 6-Chloro-2-[(2,2-dimethylpropanoyl)amino[ptcridin-4(3/7)-one (1) General Procedure 149... 

Dimethylpropanoyl)aBiino)-6-[(hydroxyintino)inethyl pteridiii-4(3//)-one (3) Single Procedure 254... 

A. 2-(2,2-Dimethylpropanoyl)-1,3-dithiane. To 43.0 g (0.358 mol) of 1,3-dithiane (Note 1) at 0°C under a nitrogen atmosphere is added 396 mL of a 1 M solution of sodium hexamethyldisilazide in tetrahydrofuran (THF) (Notes 2 and 3). The resulting yellow solution is allowed to reach room temperature and then stirred at room... 

B. anti- and syn-1S-(2,2-Dimethylpropanoyl)-1,3-dithiane 1-oxide. (+)-[(8,8-Dimethoxycamphoryl)sulfonyl]oxaziridine (51.0 g, 0.176 mol) (Note 9) is added to a cooled, stirred solution of 36.0 g (0.176 mol) of 2-(2,2-dimethylpropanoyl)-1,3-dithiane in 1000 mL of carbon tetrachloride (Note 10) at 0°C. The reaction mixture is allowed to reach room temperature, and stirring is continued at room temperature for a further 48 hr. The reaction mixture is filtered to remove the bulk of the (+)-[(8,8-dimethoxycamphoryl)sulfonyl]imine, and the filtrate is evaporated to dryness under reduced pressure. The residue is purified by passage through a short column of silica gel using dichloromethane as initial eluant to remove residual (+)-[(8,8-dimethoxycamphoryl)sulfonyl]imine. The column is then flushed with ethyl acetate to give 29.8-33.5 g (77-86%) of an ca. 3 1 mixture of anti- and syn-lS-(2,2-dimethylpropanoyl)-1,3-dithiane 1-oxide as a colorless crystalline solid, mp 103-105°C (Note 11). 

---