β-Lactam-Forming Photochemical Reactions of N-Trimethylsilylmethyl- and N-Tributylstannylmethyl-Substituted α-Ketoamides

Abstract

Two mechanisms have been proposed for the beta-lactam-forming photochemical reactions of alpha-ketoamides. One, suggested by Aoyama, involves excited-state H-atom abstraction while the other, put forth by Whitten, follows a sequential SET-proton-transfer route. The photochemical properties of N-trimethylsilylmethyl- and N-tributylstannylmethyl-substituted alpha-ketoamides were explored in order to gain information about the mechanism of this process and to develop a regioselective method for beta-lactam formation. The results of this effort show that (1) photoreactions of N-trimethylsilylmethyl-substituted alpha-ketoamides proceed by competitive H-atom abstraction and sequential SET-desilylation pathways and (2) a sequential SET-destannylation pathway is preferentially followed in photochemical reactions of the tributylstannylmethyl-substituted alpha-ketoamides.

Thelepamide: An Unprecedented Ketide-Amino Acid from Thelepus crispus, a Marine Annelid Worm

“…Another set of benchmark oxazolidinones ( 3a and 3b ) isomers possessing varrying ring substituents, and prepared by different compounds consisted of two known synthetic methods. 13 Again, NMR spectral data of 3a and 3b displayed a similar set of chemical shifts (see Figure 2B) which were also similar in comparison to the corresponding atoms in 1 . These data further justified the connectivities proposed for the heterocyclic ring.…”

Crystallization of chiral molecular compounds: what can be learned from the Cambridge Structural Database?

“…there is an inversion centre (as in e.g. AVAJAI; Wang et al, 2004) or a mirror plane (as in e.g. CATNEQ; Sellner et al, 1983) as an inner symmetry element of the molecule, but this is not always true.…”

Medium Effects on Zwitterionic-Biradicaloid Intermediates from Two Phenyl--α-oxoamides. Irradiations in Fluid and Solid Protic Media, Neat Solid Phases, and the Solid, Smectic and Isotropic Phases of a Completely Saturated Phosphonium Salt at Different Te

“…Aryl α‐oxoamides which are constrained to cisoid conformations undergo electron and rapid subsequent intermolecular proton transfer from their excited triplet states (11). Aryl α‐oxoamides capable of adopting transoid conformations undergo photoreaction efficiently through a complicated excited singlet‐state mechanism in which products are derived in parallel from both biradicaloid and zwitterionic intermediates, some of which interconvert via large conformational changes (Scheme 1) (12–18). Because it is known that the reaction intermediates are too short‐lived to diffuse appreciably before yielding products (18), the distribution of the photoproducts derived from them should be very sensitive to the polarity and microviscosity of the local environments where the reactant molecules undergo excitation; the location of the α‐oxoamides at the moment of their excitation determines primarily where they react.…”