jp508414r_si_001.pdf (1.42 MB)
Opening Access to New Chiral Macrocycles: From Allenes to Spiranes
journal contribution
posted on 2015-03-05, 00:00 authored by Silvia Castro-Fernández, María Magdalena Cid, Carlos Silva López, José Lorenzo Alonso-GómezChiral
macrocycles offer great potential and versatility regarding their
applications. They have been employed in asymmetric catalysts, as
chiral sensors, and as chiral supramolecular frameworks. For these
reasons, they have been attracting increasing interest over the years.
Despite all of the work developed in this area, most of the reported
chiral macrocycles are not conformationally stable and present weak
chiroptical responses. Such features substantially limit the scope
of applications for these compounds. On the other hand, we have shown
that axially chiral allenes can be introduced into macrocycles, conferring
conformational stability and outstanding chiroptical responses. However,
these allenes photoisomerize when conjugated with electron-donating
groups, hampering the possibility of synthesizing systems with tuned
optical properties. To overcome all of these limitations with a single
structural motif, we propose the use of spiranes to construct new
stable, conformationally rigid, and chemically functionalizable macrocyclic
structures with strong chiroptical responses. As a first step in this
new direction, we theoretically predict the chiroptical responses
for macrocycles bearing spiranes to be as strong as with their allenic
counterparts. As a side product, we also test the popular Minnesota
functional, M06-2X, and compare it with cam-B3LYP, which has been
previously analyzed with respect to experimental data in our laboratory.
Thus, we hereby propose that spiranes are a good alternative to allenes
for the construction of new chiral macrocycles.