Tetrathiacrown ethers

Analogomly, starting from l,3-dichloro-2-methylenepropane and LI373 the tetrathiacrown ether L1374 was assembled in 70 /o yield (Eq. 6.33) [104],... 

All the thiacrown ethers described so far are synthesised by stoichiometric reactions between the corresponding ligsons. However, a few examples of catalytic formation of polythiamacrocycles are well documented. It has also been reported that, in the presence of the Lewis acid BF3-Et20, l,4-dihydro-2,3-benzodithiin reacts with alkenes to give mixtures of 2 4- 2 and 1 + 1 macrocyclic tetrathiacrown ethers [132]. In the presence of a catalytic amount of Lewis acid the 1 + 1 macrocycle is the only product isolated (68% yield). 

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