Stryker s reagent

Copper hydride species, notably Stryker s reagent [Ph3PCuH]6, are capable of promoting the conjugate reduction of a,( >-unsalurated carbonyl compounds [42], Taking advantage of this trustworthy method, Chiu et al. demonstrated in 1998 an intramolecular reductive aldol reaction in the synthesis of novel terpenoid pseudolaric acids isolated from Chinese folk medicine (Scheme 28) [43]. Two equivalents of [Ph3PCuH]6 enabled cycli-zation of keto-enone 104 to provide the bicyclic diastereomers 105 (66%) and 106 (16%). The reaction also was applied to the transformation of 107... 

Scheme 29 Reductive aldol cydization of alkyne-diones catalyzed by Stryker s reagent...

Chiu et al. developed the first example of a reductive intramolecular Henry reaction induced by Stryker s reagent (Scheme 30) [53]. The conjugate reduction of keto-nitroalkenes with [Ph3PCuH]6 (150 mol%) triggers spontaneous nitro-aldol reaction at - 40 °C to produce (f-hydroxy nitro compounds in moderate yield. 

Recently, the silane-mediated reductive cyclization of activated alkynes with tethered ketones using Stryker s reagent as a catalyst was reported.112,90b Alkynyl ketone substrate 84a was treated with a catalytic amount of Stryker s reagent in the presence of polymethylhydrosiloxane (PMHS) to afford the cA-fused hydrindane 84b as a single diastereomer. This method is applicable to both five- and six-membered ring formation, but often suffers from competitive over-reduction of the reaction products (Scheme 59). 

Scheme 2.15 Reduction of propargyl acetates to terminal allenes with Stryker s reagent.

With these new levels of appreciation of the nuances associated with CuH-phosphine interactions, considerable fine-tuning of Stryker s reagent is now possible. One case in point involves enone 14, which can be converted predominately into any one of three possible products (Scheme 5.6) [40]. 

Scheme 5.7. Effect of DPPF on reductions with Stryker s reagent.

Another, albeit less-frequently employed option for a copper-mediated reduction of propargylic electrophiles to allenes relies upon the use of a copper hydride, for example, Stryker s reagent [(Ph3P)CuH]6. This reagent was applied by Brummond and Lu147 to the synthesis of the structurally complex precursor 197 for a potent antitumor agent, ( )-hydroxymethylacylfulvalene, from propargyl acetate 196 (Equation (11)). 

Sdieme 5.7. EfFect of DPPF or reductiors with Stryker s reagent. 

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