Chelation-assisted intramolecular hydroacylation: synthesis of medium ring sulfur heterocycles

Chelation‐Controlled Intermolecular Hydroacylation: Direct Addition of Alkyl Aldehydes to Functionalized Alkenes

“…The analogous b-methoxypropanal produced small amounts of the desired adduct but the major pathway remained decarbonylation (Table 1, entry 3). [14] To obtain a stronger chelating interaction, we next examined sulfide-substituted aldehydes; [15] the reaction of b-methylsulfanyl aldehyde 3 with methyl acrylate at 40 8C produced the hydroacylation adduct in 36 % yield along with side product (27 %) that originates from a Tischenko-type process (Table 1, entry 4). [16] When dichloroethane was used as solvent and the reaction temperature was raised to 60 8C, the amount of side product decreased to < 3 % and the conversion into the desired adduct increased to 96 % (Table 1, entry 5).…”

Rhodium‐Catalyzed Intramolecular Hydroacylation of 5‐ and 6‐Alkynals: Convenient Synthesis of α‐Alkylidenecycloalkanones and Cycloalkenones

“…[4] Extension of this method to the synthesis of larger cyclic compounds was accomplished by the use of 4,6-dienals or cyclopropyl-4-alkenals as reaction substrates. [5,6] Synthesis of cycloheptenones was carried out by rhodium-catalyzed intramolecular hydroacylation of 4,6-dienals;…”

Asymmetric Rh-Catalyzed Intermolecular Hydroacylation of 1,5-Hexadiene with Salicylaldehyde

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Rh-catalyzed intramolecular [1][2][3][4][5][6][7] and intermolecular hydroacylations [8][9][10][11][12][13][14][15][16][17][18][19] have recently been the focus of synthetic organic and organometallic chemists. Although Rh-catalyzed asymmetric intramolecular hydroacylation (asymmetric cyclization) has been extensively studied by us, [20][21][22][23][24] and other groups, [25][26][27][28] Rh-catalyzed asymmetric intermolecular hydroacylation has attracted only limited attention, 29-31) except for asymmetric hydroformylation.

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“…In contrast, the addition of silver salt would change the property of Rh-complex to a cationic species to accelerate the reaction. Unfortunately, the addition of bases, such as K 2 CO 3 , KOAc, and NaOAc, did not improve the yield (entries [3][4][5], and the addition of silver salts, such as AgClO 4 and CF 3 CO 2 Ag, improved the yield of products but their specific rotations were zero, meaning that the products were racemic (entries 6-8). Finally, it was found that the addition of Lewis acid improved the yield of products (entries 9-12); in particular, the addition of Zn(OTf) 2 (0.20 eq) improved the yield of product and its specific rotation showed Ϫ26°(entry 11).…”

“…Therefore, the enantiomeric excess of iso-3 could not be directly determined by HPLC using a chiral column. Thus, the mixture of products was hydrogenated by H 2 /5% Pd-C to produce saturated hydroacylated products iso- 4 a) Specific rotation of the mixture of products. b) Reaction at 50°C afforded a mixture of products in 15% yield.…”