[reaction: see text] When subjected to palladium-catalyzed amidation conditions, 2-triflyloxy phenethyl carbonates undergo, in addition to the expected aryl cross-coupling, an additional amidation with net displacement of the carbonate. The result is a one-step synthesis of indolines which may be oxidized to indoles. The utility of the procedure is illustrated by the two- or three-step syntheses of anhydrolycorinone, hippadine, oxoassoanine, and pratosine.
Anhydrous magnesium iodide (MgI(2)) is shown to be an effective promoter of the "homo 3+2" dipolar cycloaddition of nitrones with 1,1-cyclopropane diesters. In almost all cases the products tetrahydro-1,2-oxazines are formed in excellent yields. The reactions are highly diastereoselective for a cis relationship between the substitutents at the 3- and 6-positions on the tetrahydrooxazine ring. As an alternative to using a preformed nitrone, the reaction may be performed in a 3-component sense by combining an aldehyde, an hydroxylamine, and the cyclopropane in the presence of catalytic MgI(2).
Sluggish or impractical Diels−Alder reactions of a maleimide modified-MPN with a series of dienes of varying electronic and steric demands at ambient pressure and temperature proceed under hyperbaric conditions in less than 10 min without altering the gold core of the nanoparticle or its inherent physical properties.
A maleimide-modified 2.5 +/- 0.5 nm mixed monolayer protected gold nanoparticle (2-C(12)MPGN) containing approximately 30% maleimide-terminated dodecanethiolate/dodecanethiolate ligands was prepared. The 2-C(12)MPGN was reacted with a series of nitrones (a-i) at both atmospheric and hyperbaric (11 000 atm) conditions to form the corresponding isoxazolidine-modified nanoparticles (3-C(12)MPGN) via an interfacial 1,3-dipolar cycloaddition. At atmospheric pressures, the reaction proceeds slowly (if at all) and makes this reaction impractical for the synthetic modification of the nanoparticles. However, by performing the reaction under the high-pressure conditions, the reaction proceeds efficiently and quantitatively. TEM shows that the use of high pressure does not affect the size of the gold nanoparticle core. The 3-C(12)MPGNs were characterized by (1)H NMR spectroscopy by comparing the spectra obtained with those of model reactions utilizing N-dodecylmaleimide (4) with the same nitrones (a-i) to form 5. Additionally, the cycloaddition reaction also occurs more readily with 4 than with 2-C(12)MPGN with all nitrones, indicating that the environment of the latter affects the cycloaddition reaction.
CC-1065 and the related duocarmycins are members of a structurally unique family of naturally occurring molecules and remain some of the most rigorously studied antitumor compounds to date. Herein we describe a total synthesis of the (+/-)-CC-1065 CPI subunit in an overall yield of 9.3% from commercially available 5-fluoro-2-nitrophenol. The key steps of this synthesis are a Diels-Alder reaction of an o-benzoxy-monoimine quinoid and an intramolecular aryl triflate amidation, which formed the pyrrolo[3,2-f]tetrahydroquinoline intermediate en route to CPI.
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