Keywords: Kinetics / Linear free-energy relationships / Carbocations / Electrophilic additions / Nucleophilic additionsThe kinetics of the reactions of the flavylium ion 1a and the 4Ј-methoxyflavylium ion 1b with various π-nucleophiles and tributylstannane were investigated photometrically in dichloromethane. Electrophilicity parameters E(1a) = −3.46 and [a]
Triarylallyl cations react with 1,3-dienes to give Diels-Alder products in low to moderate yields. The observed second-order rate constants agree with those calculated for the stepwise processes by the correlation log k(20 ЊC) = s(N ϩ E ) [eqn. (1)] indicating the absence of a significant free energy of concert. Eqn. (1) can, therefore, also be employed for the prediction of absolute rate constants of Diels-Alder reactions of allyl cations. Scheme 2 Stepwise and concerted pathways of the Diels-Alder reactions of allyl cations 1 with dienes 2.
The developmental process for drug substances, as carried out in a medium-sized company is described. A cascade approach, ranging from route selection to commercial production and the corresponding intermediate steps, is discussed. A concerted teamwork is essential for optimal results,
and the roles and activities of the team members are outlined.
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