Synthesis of Doubly Unsaturated Aldehydes and Ketones by a Novel β‐Decarbopalladation

Abstract

COMMUNICATIONS stein-Leopoldshafen (Germany), on quoting the depository number CSD-406925. Space group I4,/ucd, u = b = 1505.2(1), c = 4747.4(6) pm, V = 10756(2) A', Z = 8, pCDLEd =1.044 gcm-', 193 K, 5173 measured reflections, 2363 unique reflections, [R,,, = 0.0261, 1855 with FO>40(F,), 210 parameters,

Palladium-catalyzed 1,3-diol fragmentation: synthesis of ω-dienyl aldehydes

“…In this context, the high yield for formation of 2a from a mixture of syn-1a and anti-1a (entry 1, Table 2) clearly indicates the superiority of the present dehydration fragmentation method over the decarboxylation method. 3,4 A similar discussion may hold for other bicyclic diols in Table 2. Particularly, the example shown in entry 11, Table 2 may highlight the utility of the present dehydration method; a diol syn-1k was produced exclusively as a single diastereomer in an 85-95% overall yield through the crossaldol reaction of the lithium enolate of nopinone with acrolein and then LiAlH 4 reduction.…”

“…Just 10 years ago, we reported that under the catalysis of palladium(0) a variety of cyclic carbonates 3 could be smoothly transformed into 2 in good yields via decarboxylative fragmentation, triggered by oxidative addition of Pd(0) to the allylic C-O bond (Scheme 1). 3 Very recently nickel(0) catalysts have been proven to work similarly well or much better, providing 2 in excellent yields and with higher E-selectivity regarding the diene moiety. 4 Here, we would like to disclose a new and efficient short cut to the v-dienyl aldehydes 2 from diols 1 based on palladiumcatalyzed dehydration fragmentation (Scheme 1).…”

Aldol elaboration of 4,5,6,7-tetrahydroisoxazolo[4,3-c]pyridin-4-ones, masked precursors to acylpyridones

“…The aldehyde 12 required for the 3-alkenyl side chain of triene 11 was prepared in four steps by the route shown in Scheme 3 , involving palladium-catalysed decarboxylative ring opening of cyclic carbonates [ 23 ]. Thus the enolate of α-tetralone was added to propenal in an aldol addition (LDA, THF, −78 °C; 86%).…”

Activation of Allyl Alcohols as Allyl Cations, Allyl Anions, and Amphiphilic Allylic Species by Palladium

“…[23] In 1997 we reported a novel palladium-catalyzed C-C bond cleavage reaction of bicyclic carbonates 11 (Scheme 15), in which 2-oxapalladacyclopentanes, formed by oxidative addition of a Pd 0 species to an allylic C-O bond and decarboxylation, undergo β-C elimination to yield ω-dienyl aldehydes. [24] The reaction can be performed with direct use of diols 12, precursors of bicyclic carbonates 12, as the starting materials. [25] The key stage in the reaction is the activation of the allyl alcohol moiety of 12 to generate π-allylpalladium, which could be achieved by use of a rather special borane reagent, 9-phenyl-9-borabicyclononane (9-Ph-9-BBN), as a Lewis acid catalyst.…”