6 research outputs found
Preparation of Tetrasubstituted 3‑Phosphonopyrroles through Hydroamination: Scope and Limitations
Phosphonylated
pyrroles were obtained by a ZnCl<sub>2</sub>-catalyzed
5-<i>exo</i>-<i>dig</i> hydroamination of propargylic
enamines. These starting compounds were obtained in two steps from
commercially available β-ketophosphonates. The method tolerates
a wide variety of substituents at the 1,2- and 5-position of the pyrrole,
while further derivatization allows for the introduction of substituents
at the 4-position via lithiation or halogenation
Synthetic Entry into 1‑Phosphono-3-azabicyclo[3.1.0]hexanes
3-AzabicycloÂ[3.1.0]Âhex-2-en-1-yl
phosphonates were prepared in
a five-step reaction route from β-ketophosphonates. The key
steps in this sequence are an atom-transfer radical cyclization and
an unforeseen lithium–halogen exchange with <i>n</i>-BuLi. The cyclization reaction proceeds with excellent diastereoselectivity.
The resulting cyclic imines were reduced, and 3-azabicyclo[3.1.0]Âhexan-1-yl
phosphonates were obtained
3‑Imidoallenylphosphonates: <i>In Situ</i> Formation and β‑Alkoxylation
3-Imidoallenylphosphonates,
allenes bearing both an electron-withdrawing
and -donating group, were isolated for the first time. An alkoxy substituent
was introduced into these unprecedented intermediates in a one-pot
approach, yielding β-functionalized aminophosphonates in excellent
yields and short reaction times. The mechanistic insights gained are
important additions to the domain of allene chemistry. Addition of
biologically important molecules, including monoglycerides, amino
acids, and nucleosides, proves the general applicability of the developed
method
Tandem Addition of Phosphite Nucleophiles Across Unsaturated Nitrogen-Containing Systems: Mechanistic Insights on Regioselectivity
The addition of phosphite nucleophiles
across linear unsaturated imines is a powerful and atom-economical
methodology for the synthesis of aminophosphonates. These products
are of interest from both a biological and a synthetic point of view:
they act as amino acid transition state analogs and Horner–Wadsworth–Emmons
reagents, respectively. In this work the reaction between dialkyl
trimethylsilyl phosphites and <i>α,β,γ,δ</i>-diunsaturated imines was evaluated as a continuation of our previous
efforts in the field. As such, the first conjugate 1,6-addition of
a phosphite nucleophile across a linear unsaturated <i>N</i>-containing system is reported herein. Theoretical calculations were
performed to rationalize the observed regioselectivites and to shed
light on the proposed mechanism
Preparation of tetrasubstituted 3-phosphonopyrroles through hydroamination: scope and limitations
Phosphonylated pyrroles were obtained by a ZnCl2-catalyzed 5-exo-dig hydroamination of propargylic enamines. These starting compounds were obtained in two steps from commercially available beta-ketophosphonates. The method tolerates a wide variety of substituents at the 1,2- and 5-position of the pyrrole, while further derivatization allows for the introduction of substituents at the 4-position via lithiation or halogenation