New directions in the condensation reactions of cyclohexanone and its Mannich base

Abstract

An unusual direction was found in the condensation of cyclohexanone and its Mannich base, leading to the formation of previously unknown polycyclic spirohydrochromans. The structure of the compounds was confirmed by 13C NMR and mass spectrometry.Carbonyl-containing spirohydrochromans have become available as a result of the discovery of the ability of t~,flunsaturated ketones to enter into dimerization of the 1,4-addition type. Its characteristics and mechanism were discussed in detail in the review [1]. In [2][3][4] it was shown that the Mannich bases of cyclic ketones can act as synthons during their thermal decomposition, vacuum distillation [5][6][7], steam distillation [8], or acetolysis in acetic anhydride in the presence of sodium aceta.te [9, 10]. In view of the prospects concerning the scientific and applied aspects of compounds of this series we continued to develop optimum conditions of synthesis and investigate features of the transformations with regard to the existence of several reaction centers in the molecule.The methods that we proposed for the benzannellated analog The yield of the product amounted to 57-64%, depending on the conditions [boiling the base (II) in toluene in the presence of hydroquinone, boiling the methiodide of (II) in DMFA with 40% potassium hydroxide, or steam distillation of the hydrochloride of (II)].Compound (I) was oximated in order to confLrm the presence of the C------O group in the molecule. Here it was established that the direction of the reaction was determined by the order in which the reagents (NH2OH.HCI, KOH) were added. If hydroxylamine hydrochloride is added to a water-alcohol alkaline solution of the dimer of (I), the oxime (llI) is formed. Addition of the reagents in the reverse order leads to the formation of 2, 16-dioxatetracyclo[7.6.1.03,8.01,11]hexadecan_ 3-ol (IV) with a 64 % yield.

Concise assembly of 7-ethynyl-6,8-dioxabicyclo[3.2.1]octanes from acetylenes and ketones

“…13 Notably, 2-acyldihydropyrans were popular starting materials for the synthesis of 7-alkyl DOBCOs via reduction of the keto group and ring closure of the forming alcohols. 14 However, this approach did not cover DOBCO derivatives with unsaturated, especially acetylenic, functions, albeit the latter were of particular importance in opening the door to rich acetylene chemistry.…”