Aldehydes cyclization, regiochemistry

Lalande and coworkers have studied the regiochemistry of cyclization of keto aldehyde (44 equation 107). In this system, aqueous KOH gives exclusively the cyclopentenyl methyl ketone (45), while piperidinium acetate leads to cyclopentenecarbaldehyde (46). Similar results were obtained by Wolinsky with the isopropenyl analog of (44). These examples also demonstrate the preference for formation of a five- over a seven-membered ring. 

Aldehyde, Ketone, and Ester Enolates 867 Enolate Regiochemistry 872 The Aldol Condensation 873 Mixed Aldol Condensations 878 Chalcones From the Mulberry Tree to Cancer Chemotherapy 880 The Claisen Condensation 882 Intramolecular Claisen Condensation The Dieckmann Cyclization 884 Mixed Claisen Condensations 885 Acylation of Ketones with Esters 886 Alkylation of Enolates 887 The Acetoacetic Ester Synthesis 889 The Malonic Ester Synthesis 891 Alkylation of Chiral Enolates 893 Enolization and Enol Content 895 a Halogenation of Aldehydes and Ketones 900... 

The Ni(COD)2-catalyzed intramolecular cyclizations of aldehyde and alkyne in the presence of vinylzirconiums proceed smoothly to give azadecalin in satisfactory yield. Interestingly, the regiochemistry of alkyne insertion is opposite to that of aldehyde/alkyne/organozinc three component couplings [199]. 

---