One-pot synthesis of multi-substituted conjugated dienones by trapping allene carbocations with active ylides

Abstract

An Rh (II)/boron reagents co-catalyzed unprecedent transformation was established for a rapid construction of multi-substituted conjugated dienones under a mild condition by trapping allene carbocations with oxonium ylides from simple...

Highlighting the Rich Chemistry of the Allenone Moiety

“…Alkynols 606 react with acids generating allene carbocations 611 , which can be trapped by oxonium ylides (formed in situ from alcohols and diazoketones 607 ) providing the observed conjugate dienones 610 , which are generated from the tautomerization of intermediate allenones 609 (Scheme 103). [258] The transformation provides compounds 610 with good yields and Z/E ratios up to 25:75 (Scheme 103). [258] …”

“… [258] The transformation provides compounds 610 with good yields and Z/E ratios up to 25:75 (Scheme 103). [258] …”

“…[146] In the presence of optically pure phosphine 254, enantioenriched spirocyclic compounds 255 have been accessed using oxindoles 253 as nucleophiles (Scheme 50b). [147] In a different report, cyclopentenes 259 and methylene cyclopentanes 260 have been obtained through a base-promoted multicomponent reaction involving allenones 2, ethyl 4-chloro-3-oxobutanoate (257) and malononitrile or cyanoacetate (258) as nucleophiles (Scheme 51a). [148] The proposed reaction sequence starts with the S N reaction of ethyl 4-chloro- served adducts 259.…”

Efficient synthesis of benzosultams containing continuous quaternary carbons via trapping active ylides with cyclic N-sulfonyl ketimines

“…20 The reactivity strongly depends on the nature of electrophiles which tend to be activated by Brønsted or Lewis acids for matched reactivity. 21 With our continuous efforts in studying the chemical transitions of active ylide intermediates, 21,22 we envisioned that N-sulfonyl ketimines may be used as a suitable electrophile to capture onium ylides and construct benzosultams containing continuous quaternary carbon centers. Although several reactions of active ylides with aromatic imides have been efficiently developed, 23 the desired reaction is still challenging due to the much stronger electrophilicity and higher steric hindrance of N-sulfonyl ketimines than that of aromatic imides, which will lead to a mismatch of the reactivity.…”

“…20 The reactivity strongly depends on the nature of electrophiles which tend to be activated by Brønsted or Lewis acids for matched reactivity. 21…”