Approach to the tricyclic core of the tigliane-daphnane diterpenes. Concerning the utility of transannular aldol additions.

Two transannular (TA) aldol reactions were used to assemble the tricyclic carbon skeleton found in the tigliane and daphnane classes of diterpene natural products.

The oxidative mannich reaction catalyzed by dirhodium caprolactamate.

Dirhodium caprolactamate [Rh2(cap)4] is a highly effective catalyst for the oxidative Mannich reaction. The reaction proceeds via C-H oxidation of a tertiary amine followed by nucleophilic capture. This green transformation is conducted in protic solvent using inexpensive T-HYDRO (70% t-BuOOH in water). Synthetically valuable gamma-aminoalkyl butenolides are obtained.

Benzylic oxidation catalyzed by dirhodium(II,III) caprolactamate.

[reaction: see text] Dirhodium caprolactamate [Rh2(cap)4] is an effective catalyst for benzylic oxidation with tert-butyl hydroperoxide (TBHP) under mild conditions. Sodium bicarbonate is the optimal base additive for substrate conversion. Benzylic carbonyl compounds are readily obtained, and a formal synthesis of palmarumycin CP2 using this methodology is described.

Efficient aziridination of olefins catalyzed by mixed-valent dirhodium(II,III) caprolactamate.

[reaction: see text] A mild, efficient, and selective aziridination of olefins catalyzed by dirhodium(II) caprolactamate [Rh(2)(cap)(4).2CH(3)CN] is described. Use of p-toluenesulfonamide (TsNH(2)), N-bromosuccinimide (NBS), and potassium carbonate readily affords aziridines in isolated yields of up to 95% under extremely mild conditions with as little as 0.01 mol % Rh(2)(cap)(4). Aziridine formation occurs through Rh(2)(5+)-catalyzed aminobromination and subsequent base-induced ring closure. An X-ray crystal structure of a Rh(2)(5+) halide complex, formed from the reaction between Rh(2)(cap)(4) and N-chlorosuccinimide, has been obtained.

Dirhodium(II) caprolactamate: an exceptional catalyst for allylic oxidation.

The oxidation of organic molecules represents a fundamentally important chemical process. Particularly important is allylic oxidation, whereby a single methylene unit is converted directly into a carbonyl group. In this communication, we report that dirhodium(II) caprolactamate [Rh2(cap)4] in combination with tert-butyl hydroperoxide (terminal oxidant) effectively catalyzes the allylic oxidation of a variety of olefins and enones. The reaction is completely selective, tolerant of air/moisture, and can be performed with as little as 0.1 mol % catalyst in minutes. A mechanistic proposal involving redox chain catalysis has been put forth, as well as evidence for the intermediacy of a higher valent dirhodium tert-butyl peroxy complex.