Synthesis of tetrahydroisoquinocarbazoles via C-2 alkylation of indoles with 2-alkoxycyclopropanoate esters.

A concise method for the synthesis of several tetrahydroisoquinocarbazole derivatives is reported, where the core is prepared in six steps from tryptophol in 51% overall yield. The pentacyclic analogs are constructed via a dipolar C-2 alkylation of a 3-substituted indole with a 2-alkoxycyclopropanoate ester and a SmBr(2)-HMPA mediated ketyl-alkene ring closure

BF2OBn∙OEt2: A Novel Lewis Acid and its use in a Regio- and Stereo-selective Opening of Trisubstituted Epoxides and its Application Towards Amphidinolide C

The generation of a new Lewis acid (BF2OBn·OEt2) has been reported, and its usefulness has been demonstrated in the regio- and stereoselective ring-opening of trisubstituted epoxides. This Lewis acid is one in a series of new Lewis acids generated from BF3·OEt2 that display varying levels of Lewis acidity. When paired with a modified Shi epoxidation protocol, highly functionalized propionate units, such as those found in a wide variety of natural products, can be accessed. In conjunction with a Mukaiyama oxidative cyclization employing our second generation catalyst Co(nmp)2, this procedure ultimately culminated in the shortest and highest yielding route towards the methyl-substituted trans-tetrahydrofuran (trans-THF) fragment present in amphidinolide C, C2, and F

First total synthesis and structural reassignment of (-)-aplysiallene.

The first total synthesis of (-)-aplysiallene has been completed in 16 steps and features a key sequential Mukaiyama aerobic oxidative cyclization to prepare the fused bis-THF core. The original stereochemical assignment has been revised as shown

Total synthesis of (+/-)-goniomitine via a formal nitrile/donor-acceptor cyclopropane [3 + 2] cyclization.

The total synthesis of (+/-)-goniomitine has been accomplished in 17 linear steps with 5.2% overall yield starting from commercially available delta-valerolactam. A synthetic highlight includes the first application of a formal [3 + 2] cycloaddition between a highly functionalized nitrile and a donor-acceptor cyclopropane to prepare an indole nucleus. The use of a microwave reactor is shown to greatly improve the reaction times for two steps

Gram scale synthesis of the C(1)-C(9) fragment of amphidinolide C

An allylic cis-epoxide prepared by Sharpless asymmetric epoxidation was transformed in 9 steps and 41% overall yield to the cyclization precursor 4 via a key one carbon homologation. Cobalt catalyzed aerobic oxidative cyclization of 4 gave the trans-THF in 94% yield at gram scale. Subsequent manipulations, including a Still-Gennari olefination, Sharpless asymmetric dihydroxylation, Corey-Fuchs alkynylation and Kazmaier hydrostannylation provided the fully functionalized C(1)-C(9) fragment 2 suitable for cross coupling. The sequence is readily scalable and provides gram quantities of

Diels-Alder chemistry of siloles and their transformation into cyclohex-2-ene-1,4-cis-diols.

The synthesis of siloles with substitution patterns that are continuative toward natural product synthesis are described. Their reactivity in Diels-Alder chemistry was explored through thermal, Lewis acid, and high-pressure reactions. Furthermore, bicyclic adducts were oxidatively cleaved to reveal a highly functionalized cyclohexene core

Gram scale synthesis of the C(18)-C(34) fragment of amphidinolide C.

The synthesis of the C(18)-C(34) fragment of amphidinolide C has been achieved via two routes, culminating in both the shortest (11 steps) and highest yielding (26% overall yield) approaches to this segment. The highly convergent approach will facilitate the synthesis of analogues, including the C(18)-C(29) fragment of amphidinolide F. Synthetic highlights include the selective methylation of a diyne, and the highly efficient use of a second generation cobalt catalyst in the Mukaiyama oxidative cyclization to form the trans-THF ring

Silole based acetylenes as advanced π-conjugated systems for optoelectronic applications

Nonlinear optical (NLO) and electro-optical (EO) properties of π-conjugated systems have been the subject of intense interest during the past several decades. In this mini-review we focus on semiconducting materials based on alkyne π-conjugation, with particular emphasis on those examples from our laboratory of chromophores containing a silole core. Several closely related examples from the literature are also discussed

Ytterbium triflate catalyzed synthesis of alkoxy-substituted donor-acceptor cyclobutanes and their formal [4 + 2] cycloaddition with imines: stereoselective synthesis of piperidines.

A new synthesis of 2-alkoxy-1,1-cyclobutane diesters and their first use in dipolar cycloadditions is reported. Both the formation of the donor-acceptor cyclobutanes and their subsequent annulation with in situ formed imines are catalyzed by Yb(OTf)(3). Cyclobutanes with carbon donor groups give piperidines with high trans stereoselectivity