Synthesis of angularly fused cyclopentanoids and analogous tricycles via photoinduced ketyl radical/radical anion fragmentation–cyclization reactions

Expansion of Structure Property in Cascade Nazarov Cyclization and Cycloexpansion Reaction to Diverse Angular Tricycles and Total Synthesis of Nominal Madreporanone

A cascade Nazarov cyclization/dicycloexpansions reaction was developed for the precise synthesis of the angularly fused M/5/N (M=5, 6; N=4-9, 13) tricyclic skeletons. The prioritized expansion of the first ring played a critical role in the transformations, due to the release of ring strain, and the nature of the substituents present on the substrate is another influencing factor. This pioneering cascade reaction features broad substrates scope (33 examples), short reaction time, exceptional yields (up to 95 %), and remarkable regioselectivities (>20 : 1). Exploiting the synthetic application of this cascade reaction, we successfully executed a succinct total synthesis of nominal madreporanone for the first time.

Access to P-chiral sec- and tert-phosphine oxides enabled by Le-Phos-catalyzed asymmetric kinetic resolution

The synthesis of P-stereogenic building blocks is extremely difficult. Herein we report an efficient kinetic resolution of secondary phosphine oxides via a Le-Phos-catalyzed asymmetric allylation reaction with Morita-Baylis-Hillman carbonates. This method provides facile access to enantioenriched secondary and tertiary P-chiral phosphine oxides with broad substrate scope, both of which could serve as P-stereogenic synthons, and can be rapidly incorporated into a given scaffold bearing a P-stereocenter. The highly desirable late stage modifications demonstrate the practicability of our method and can be a critical contribution to obtaining optimal P-chiral catalysts and ligands.

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

The [2 + 2] photocycloaddition is undisputedly the most important and most frequently used photochemical reaction. In this review, it is attempted to cover all recent aspects of [2 + 2] photocycloaddition chemistry with an emphasis on synthetically relevant, regio-, and stereoselective reactions. The review aims to comprehensively discuss relevant work, which was done in the field in the last 20 years (i.e., from 1995 to 2015). Organization of the data follows a subdivision according to mechanism and substrate classes. Cu(I) and PET (photoinduced electron transfer) catalysis are treated separately in sections 2 and 4 , whereas the vast majority of photocycloaddition reactions which occur by direct excitation or sensitization are divided within section 3 into individual subsections according to the photochemically excited olefin.