Cuprates reaction with tosylates

The corresponding reaction with PlnSnM proceeds with complete inversion regardless of addition mode (equation 21). In this case, radical reactions appear unimportant. Displacement of the tosylate by a trimethyltin cuprate was also found to take place by inversion. 

The 13,17-seco-acid lactone (258), obtained from a Baeyer-Villiger oxidation of 5a-androstan-17-one has been reduced to yield 13,17-seco-5a-androstan-13a,17-diol, whose diacetate on pyrolysis furnished the endocyclic seco-olefin (259 R = OAc) as the major reaction product. A minor product is the corresponding A12 13-olefin.115 Hydrolysis of the acetate (259 R = OAc) to its alcohol (259 R = OH) and formation of the tosylate and the iodide (259 R = I), followed by reaction with lithium dimethylcuprate, afforded a route to A1314-13,17-seco-5a-D-homoandrostene (259 R = Me). The [17a,17a,17a-[2H3]androstene (259 R = CD3) was prepared by treating the iodide (259 R = I) with lithium perdeuteriodimethyl-cuprate. 

The tosylate group can be displaced from alkyl tosylates by dialkyl-cuprates 256, 297, 301), presumably by attack at carbon by the d electrons of copper. A transient copper(III) intermediate may be formed [Eq. (87)], as suggested for similar reactions with alkyl halides. An analogous reaction was reported between a copper(I) carboxylate and an alkyl tosylate 185). (Carboxyethyl)methylcopper, C2H5O2CCH2CU, failed to react with butyl tosylate in THF 181). However, copper compounds of the type RCu are generally less reactive than the cuprates. 

Holmes used a strategy similar to that of Silverman, just discussed, to produce longer chain amino acids. Reaction of 5.42 with tosyl chloride was followed by reaction with di-n-butyl cuprate to give 5.46. This was hydrolyzed with 2M HCl to give a quantitative yield of 4S-aminononanoic acid, 5.47. ... 

Lithium dibutylcuprate reacted with ( )-l, 3-butadienyl p-tosyl sulfone affording (Z)-2-octenyl p-tosyl sulfone. In the reaction of allyl ( )- and (Z)-l, 3-dibutadienyl sulfones with lithium dibutylcuprate or lithium (Z)-di(l-butenyl) cuprate, the major compound obtained was of (Z)-geometry around the 2,3-double bond, indicating that (Z)-selectivity is not so high in this reaction (56-79%)408-... 

The optimum results were obtained with Grignard reagents in the presence of 10 mol % of Cu(I)CN. The stereochemical course of this MIRC reaction can be explained by adopting Yamamoto s model for conjugate addition of cyano-cuprates to y-alkoxy-a,)5-unsaturated esters (Fig. 2) [35]. In this model, it is proposed that the larger substituent (L), in our case the tosyl group, will adopt the... 

A multi-step reaction sequence was then realized to prepare the precursor (178) for the pivotal macrocyclization reaction. Alternate stepwise chain elongations were achieved according to Schemes 28 and 29. Reaction of the tosylate prepared from the alcohol 162 with lithium acetylide afforded the alkyne 174 (Scheme 28). Following the introduction of a tosylate at the upper branch, a one-carbon chain elongation of the terminal alkyne afforded the methyl alkynoate 175. A methyl cuprate 1,4-addition was used to construct the tri-substituted C double bond stereoselectively. For this purpose, the alkynoate 175 was initially transformed into the Z-configured a,/ -unsat-... 

Likewise, alkynyliodonium tosylates can be coupled with dialkyl- and diphenyl cuprates 136 to afford the respective alkyl- and phenyl-substituted alkynes 137 (Scheme 56) [114]. An interesting example of this reaction involves the coupling of (trimethylsilyl)ethynyl iodonium triflate with cubyl cuprate generated in situ from iodocubane 138 [116]. 

The synthesis of ( )-pancratistatin (211) has been achieved by application of a sequence of the reactions noted previously to a [Z-O-t-butyldimethylsilyl (TBS)-4,5-methylenedioxy]phenyl derivative. Namely, coupling of N-(p-tosyl)aziridine 232 with the cuprate derivative of [3-0-TBS-2-(A(,N-dimethylcarboxamido)-4,5-methylenedioxy]benzene, in a manner similar to that noted for 210, produced N-(6-arylcyclohex-4-enyl)-N-(p-tosyl)amide as a mixture of atropisomers, reductive N-... 

The order of reactivity is I > Br > Cl. Thus the yield of (E)-2-undecene using 1-chlorooctane in DME is only 50%. Tosylates do not enter into the reaction. This reaction has also been carried out with the cuprate reagent fcHj, H ... 

---