Deacetalisation–bicyclisation routes to novel polycyclic heterocycles using stannous chloride dihydrate

Does gastric dilation predict adverse perinatal or surgical outcome in fetuses with gastroschisis?

“…5 The most general method for their synthesis, introduced in the seminal work by Meyers et al.,1, 2 wherein a γ‐ketoacid is condensed with an amino alcohol under dehydrating conditions in toluene, heated to reflux, is still, by far, the most commonly employed means of accessing the bicyclic scaffold B . Modifications have been made to the Meyers’ lactamization with the aim of introducing milder conditions;6 these modifications range from using microwave energy6a or employing Lewis acid catalysis,6b to activating the acid 6c. A second commonly employed,7 but stepwise, route to these bicyclic lactams, also originating from the Meyers’ group,2a relies heavily on N ‐acyliminium chemistry, which has been extensively elucidated by Speckamp and Hiemstra 8.…”

Preparation of Novel Polycyclic Heterocycles Using a Tin(II) Chloride Dihydrate-Mediated Deacetalisation-Bicyclisation Sequence

“…These conditions were then applied to a range of phenyl esters, 20 producing novel polycyclic heterocycles 24b-g (Scheme 8). These heterocycles all show characteristic 1 H and 13 In summary, we have developed a mild, cheap and simple method of producing a diverse range of polycyclic heterocycles from commercially available or easily accessible starting materials using amide coupling followed by a tin(II) chloride mediated deacetalisation-bicyclisation sequence. The products, several of which have been obtained in diastereoselective processes, should be of interest both in their own right and as building blocks for the production of more complex target molecules.…”

“…Preliminary results were published in a recent communication. 13 We have since carried out additional optimisation and scoping studies and now present a more detailed discussion of this one-pot, tandem deprotection-bicyclisation procedure.…”

Metal halide hydrates as lewis acid catalysts for the conjugated friedel-crafts reactions of indoles and activated olefins

“…37 The Lewis acidity of SnCl 2 ·2H 2 O has been reported by others in different reactions types. [38][39][40] Although the hydrogen Brønsted acid catalysis has been suggested by Spencer as the main process when a metal halide is used as a Lewis catalyst in aqueous (or protic alcoholic) solvents, 41 other authors postulated the water-tolerance of many metal halides. Kobayashi suggests that the certain metal halides are able to complex with the electrophile before the hydrolysis occurs.…”