Carbon tether incorporation and removal

IV.6.2 Arene Substitution Involving Temporary Incorporation and Removal of Carbon Tethers via Carbopalladation and Decarbopalladation... 

With the basic skeleton of 47 and 48 in hand, we proceeded to incorporate the tethers (Scheme 13). The three-carbon tether was attached to the helicene unit by reacting the phenol of 53 with 3-bromo-l-propanol under basic conditions. Deprotection of the acetamide in 64 with KOH at reflux afforded the desired molecular rotary motor prototype 47 as a mixture of atropisomers. In an analogous way, the two-carbon tether was introduced by reaction of the phenol 53 with the methoxymethyl (MOM) ether of 2-bromoethanol. Deacetylation with KOH (—>66) and removal of the MOM group under acidic conditions led to the two-carbon tether molecular motor prototype 48, again as a mixture of three rotamers (Scheme 13). 

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