A concise and facile synthetic protocol for the construction of the 2-γ-lactone chromanone skeleton has been achieved through a TMSI-promoted diastereoselective vinylogous Michael addition of siloxyfuran to 2-substituted chromones. The applicability of this method is demonstrated through the rapid access to the total syntheses of (±)-microdiplodiasone, (±)-lachnone C, and (±)-gonytolides C and G.

A Zn­(OTf)2-catalyzed formal [3 + 3] cascade annulation strategy for the synthesis of functionalized chromeno­[2,3-b]­pyridines has been developed using propargylic alcohols and 2-aminochromones as the substrates. The protocol provides a convenient and atom-economical method of accessing a broad range of chromeno­[2,3-b]­pyridine derivatives in excellent yields with good functional-group tolerance. The method is also effective on the gram scale, which highlights the inherent practicality of this synthetic transformation.

A one-pot Pd-catalyzed carbonylative Sonogashira coupling in tandem with double annulation reaction to synthesize benzannulated [6,6]-spiroketals from o-iodophenols and terminal alkynols or alkynyl phenols was achieved. The protocol provides straightforward and facile access to benzannulated [6,6]-spiroketals in moderate to good yields and excellent diastereoselectivities under balloon pressure of CO at room temperature. Letter pubs.acs.org/OrgLett

Herein, an organocatalytic and highly diastereoselective addition of 4-substituted oxazolones to isatinderived ketimines has been developed. This protocol provides a variety of aminooxindole-oxazolone adducts containing congested vicinal N-substituted quaternary stereogenic centers. Good yields and excellent diastereoselectivity were obtained under mild reaction conditions. 3-Substituted 3-amino-2-oxindole [1] skeleton containing a tetrasubstituted centre [2] at the 3-position has emerged as prevalent structure scaffold in a diverse range of biologically active natural products and pharmaceuticals, [3] such as the antimalarial drug candidate NITD609, [4] the vasopressin VIb receptor antagonist SSR-1494153 [5] and the potent gastrin/CCK-B receptor antagonist AG-041R ( Figure 1). [6] The organocatalytic Mannich reaction of various nucleophiles with isatin-derived ketimines is one of the most straightforward and powerful methods for the construction of 3-substituted 3-amino-2-oxindole skeletons. [7] Some successful examples have been reported for the construction of vicinal tetrasubstituted centres using isatin-derived ketimines as electrophiles. [8] On the other hand, oxazolone is a privileged heterocycle, which plays an important role in diversity-oriented syntheses of important amino acid derivatives and versatile heterocyclic compounds. [9] Very recently, the groups of Ooi, [10a] Wang, [10b] Hui, [10c] Gong, [10d] Toste [10e] and Sebesta [10f] have disclosed the additions of 4-substituted oxazolones to N-protected aldimines for the synthesis of oxazolones bearing a quaternary stereocentre, which can be transformed into quaternary α-amino acids. However, to the best of our knowledge, the addition of 4-substituted oxazolones to ketimines has not been described yet. Herein, we report an organocatalytic diastereoselective addition of 4-substituted oxazolones to isatin-derived ketimines. This new protocol provides rapid access to a range of heterocyclic compounds containing both aminooxindole and oxazolone moieties with good yields and excellent diastereoselectivity.The reaction of isatin-derived N-Boc-ketimine 1 a with oxazolone 2 a was selected as the model case to screen the reaction conditions (Table 1). To our delight, the desired product 3 a was obtained in 93% yield as a pair of inseparable diastereoisomers (42:58 dr) in the presence of 10 mol% DABCO in CH 2 Cl 2 (entry 1). 10 mol% PPh 3 could afford 3 a with better yield (98%) and better diastereoselectivity (88:12 dr) (entry 2). Subsequently, we screened a series of solvents, and found that CH 2 Cl 2 gave the best result (entries 2-7). When the reaction was [a] P. by flash chromatography on silica gel (with petroleum ether : EtOAc = 6:1 as the eluent) to afford product 3.

Complete unambiguous assignments of 1H and 13C chemical shifts for α‐tetralone, a related dihydroanthracenone and two related dihydrophenanthrones are presented. Data are based on results of 400 MHz 1H−1H and 1H−13C COSY experiments, and permit an evaluation of linear vs. angular endo and exo ketone orientation on the NMR parameters.