907-99-3Relevant academic research and scientific papers
Medium-ring Ketone Synthesis. Synthesis of Eight- to Twelve-membered Cyclic Ketones based on the Intramolecular Cyclization of Large-Membered Lactam Sulfoxides or Sulfones
Ohtsuka, Yasuo,Oishi, Takeshi
, p. 454 - 465 (2007/10/02)
An effective general method for the construction of medium-ring ketones from the corresponding ω-bromocarboxylic acids is described.When the diamide disulfide 10 was treated with NaBH4 and NaH in 2-propanol, reductive cleavage of the sulfur-sulfur bond and concomitant intramolecular coupling of the resulting thiolate anion with the terminal bromide took place and the large-ring lactam sulfide 7, which was the key intermediate for the synthesis of medium-ring ketones, was obtained.Although lithium diisopropyl amide (LDA) treatment of 11 followed by reductive desulfurization provided cycloundecanone (13d) in only 19.5percent yield, intramolecular cyclization of the α-methylated analogues 17 with LDA proceeded smoothly and the keto sulfoxides 18 were obtained in quantitative yields.In the case of the lactam sulfones 21, tert-BuOK was effective as a base for the intramolecular cyclization, affording the keto sulfones 22 in quantitative yields.The keto sulfoxides 18 and sulfones 22 were subjected to reductive desulfurization with Al-Hg to yield medium-ring ketones 19 and 13, respectively, in high yields.Keywords - medium-ring ketone; intramolecular cyclization; large-ring lactam sulfide; bis(2-methylaminophenyl) disulfide; 2-methylaminobenzenethiol; reductive desulfurization; sulfur-stabilized carbanion; active methylene
