F. Babudri

One-step synthesis of 1,n-dicarbonyl compounds from carboxylic acid derivatives and di-Grignard reagents in the presence of transition metal catalysts

Abstract The transition metal catalyzed cross-coupling reaction of alkane di-Grignard reagents with carboxylic acid derivatives provides a convenient one-step synthesis of symmetrical 1,n-diketones (n ⩾ 8) and long-chain dicarboxylic thiol esters.

Ring opening of benzothiazoles with allylic grignard reagents

Abstract A novel ring opening reaction of the benzothiazole system with allylic Grignard reagents is reported. A possible mechanism is presented.

Organometallic induced self-condensation of carboxamides

Abstract N,N-Disubstituted carboxamides containing α-hydrogen atoms undergo self-condensation reaction simply on treatment with Grignard reagents or n-BuLi in THF room temp. The reaction is considerably influenced steric hindrance at the α-carbon and the condensing agent utilized. A possble Claisen-type mechanism is also reported.

Stereoselective synthesis of 2-alkylidene-3,4-dihydro-3-oxo-2h-1,4-benzothiazines

Abstract Metallation of 4-methyl-3,4-dihydro-3-oxo--2H-1,4-benzothiazine with LDA and subsequent reaction with aldehydes leads to diastereomeric aldols 4 and 5 . Acetylation followed by acetic acid elimination of the aldols provides a stereoselective and high yield route to 2-alkylidene-3,4-dihydro-3-oxo-2H-1,4-benzothiazines.

Decomposition of arilazides and p-tosylazide by thf/n-botyllithium. A new source of diazomethmne

Abstract Variously substituted arylazides, as well as p -tosylazide, when allowed to react at room temperature with THF previously treated with n -butyllithium, undergo a rapid decomposition affording the corresponding amines and fomamides, together with diazomethane. This diazo transfer (with deformylation) reaction is thought to involve the enolate of the acetaldehyde generated by the known cycloreversion of THF in the presence on n

Acyclic stereoselection. Erythroselective aldol condensation of 4-acyl-2,3-dihydro-4h-1,4-benzothiazine and 10-acylphenothiazine.

Abstract The title amides undergo aldol-type cross-condensation providing aldols of exclusive erythro configuration. The preferred cis geometry of the precursor amide enolate is likely to be at the origin of the erythro selection.

Reactions between heteroaromatic halides and lithium dimethylcuprate; synthetic and mechanistic aspects

Abstract The reactions of halo-benzothiazoles, -pyridines and -benzofurazans with lithium dimethylcuprate have been investigated. Metal-halogen exchange usually occurs together with cross-coupling. The amount of the product derived from the latter process is increased by adding methyl iodide to the reaction mixtures. The significance of the results is discussed.

Self-condensation reaction of alkylbenzothiazoles with Grignard reagents

Abstract 2-alkylbenzothiazoles undergo Claisen-type self-condensation reaction simply on treatment with Grignard reagents.

Regioselective allylation and propargylation of pyrimidines

Abstract Reactions of pyrimidines 1a and 1b with allylic Grignard reagents 3a-f lead to allyldihydropyrimidines 2a-h and 21-n in very good yields. Dehydrogenation of 2a-d with DDQ furnished excellent yields of allylpyrimidines 1c-f . Propargylation of 1a with 3g and 3h provides propargyl dihydropyrimidines 2g and 2h respectively. 2g can be oxidised with DDQ to 1g . Allylation of 1c and 1i gives 1m and 1n respectively. Reduction of 1f leads to the branched alkyl derivative 1r .

Lithiation α to heteroatoms: eliminative ring fission of heterocycles

The behaviour of some heterocycles, having two heteroatoms in a 1,4-relationship, towards lithium di-isopropylamide (LDA) has been examined. The dihydrobenzothiazines (2a–c) and (3b), morpholine (12), benzoxazine (14), oxathiane (16), piperazine (18), tetrahydroquinoxaline (20), 1,4-dithiane (25), and dihydrodioxine (27) undergo ready ‘eliminative ring fission.’ Very marked differences have been observed for unsubstituted and substituted derivatives. Whereas the dibenzoyltetrahydroquinoxaline (20) and the dioxine (27) readily react to give ring-opened products (21) and (30) respectively, substituted derivatives (22), (23), and (32) were found to be completely unreactive.