S. Florio

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.

Lithiation of benzothiazolyl substituted epoxides and reactions with electrophiles

Abstract Deprotonation of epoxides 1 with n-BuLi or LDA at −90°C produces dark red solutions of oxiranyllithiums 2 which react with electrophiles leading to oxiranes 3 .

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.

Reversible allylic condensation of metalloallyls of heterocycles: counterion effect

Abstract Metalloallyls of benzothiazole, benzoxazole and pyrimidine 2 condense with aldehydes to furnish α-regioisomers 3 and 4 or γ-regioisomer 5 depending upon the experimental conditions and the nature of the metal of 2 . The allylic condensation of 2 with aldehydes appears to proceed with satisfactory to high syn diastereoselectivity as for the α-regioisomers; γ-regiosomers are of exclusive trans configuration.

Nickel-complex-catalyzed cross-coupling of grignard reagents with 2-halogenobenzothiazoles

Abstract 2-Halogenobenzothiazoles undergo C-C cross-coupling reaction with Grignard reagents in the presence of Ni(II)-phosphine complexes. The reaction is considerably influenced by the nature of the phosphine bonded to Ni(II) and the halogen in the halogenobenzothiazole. Particularly efficient catalysts are 2-chlorobenzothiazole coordinated nickel-complexes, NiBr 2 (H 2 O)(2-Cl-BT), NiBr 2 (2-Cl-BT)PMe 3 , NiBr 2 ,(2-Cl-BT)PCy 3 and complex NiBr 2 (DMSO)PMe 3 , which all are here reported for the first time. A possible mechanism for the catalytic activity exhibited by the nickel-complexes in the C-C cross-coupling of 2-halogenobenzothiazoles with Grignards is also reported.

Lithiation of 2-chloromethylpyridine: synthesis of 2-oxiranyl pyridines

Abstract Deprotonation of 2-chloromethylpyridine 1a with lithium diisopropylamide (LDA) in tetrahydrofuran (THF) at −78°C gives a red solution of 2-pyridylchloromethyllithium 1b , which reacts with carbonyl compounds furnishing oxiranes 2 .

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.

Stereoselective synthesis of vinylbenzothiazoles and their epoxides.

Abstract Vinylbenzothiazoles 2 were stereoselectively prepared through isomerization of allylbenzothiazoles 1 . Oxiranes 5 and 8 were synthesized from 2 and 1 via cyclization of the corresponding bromohydrins 3 , 4 , 6 and 7 .