Benzothiazole Grignard reagents

Primary allylic sulfides of derivatives of benzothiazole-2-thiol react with Grignard reagents in the presence of copper(I) iodide to yield olefins, with or without allylic rearrangement, depending on the nature of the solvent and the allylic sulfide [71 Eq. (62) and Table 14]. 

In a similar way to allylic Grignard reagents, allenyl magnesium bromide reacts with benzothiazole to give 2,2 -dithio-7V-dipropargylmethyl dianiline (51). It is noteworthy that with 2-alkylthiazoles the propargylbenzothiazoline (52) is the product of the reaction (Scheme 8) <86S638>. 

The tautomerism of hydroxythiazoles has been discussed in Section 3.06.4.4. The reactivity of hydroxythiazoles is well-documented in CHEC-I <84CHEC-I(4)285>. 2-Methoxy benzothiazole (184) has been found to react with allenylmagnesium bromide (185) to produce 2-allenylbenzothiazole (188), the formation of which can be rationalized in terms of a Sgi mechanism involving the attack of the allenic form of the Grignard reagent followed by the elimination of methanol and isomerization of the intermediate (187) (Scheme 44) <86S638>. 

The reaction of 1,3-disubstituted perhydropyrido[l,2-c][l,3]oxazines (69) and 7-(benzothiazol-l-yl)-6,7-dihydro-17/,3//,5//-pyrido[3,2,l-iy][3,l]benz-oxazine with Grignard reagents led to 2-(/V-substituted 2-piperidyl)ethanols (70) (50JA358 58CLY2081) and l-benzyl-4-(benzotriazol-l-yl)-8-hydroxy-methyl-l,2,3,4-tetrahydroquinoline (95JOC3993), respectively. 

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