Studies on synthesis of optically active twelve-membered diynes: a convergent construction of a twelve-membered diketodiyne compound with C2 symmetry

Acetylenosaccharides

“…The pioneering work in additions to fully protected aldehydo-saccharides was by Horton and co-workers [105], a typical example being the addition of HCaCsMgBr to the isopropylidenated glyceraldehyde 64 to provide a 44:56 mixture of the propargylic alcohols 65a and 65b [106] (Scheme 5.14). The yield of the desired isomer may be increased by judicious choice of the reaction conditions, as illustrated by 184 the transformation of 66 into 67a and 67b in ratios ranging from 75:25 to 40:60 [107], by the transformation of the unwanted isomer into the desired isomer through a Mitsunobu reaction (see, for example [108][109][110][111]), or by oxidation of the epimeric alcohols to the ynone followed by reduction with Selectrides [112]. The propargylic amines 69a and 69b were obtained with excellent diastereoselectivity, albeit in low to moderate yields, by the addition of Me 3 SisCaCsLi to the aldimine 68 [113].…”

“…Application of the alkynylating ring-opening of epoxides has been restricted to C 2 -symmetric diepoxides: namely the 1,2:5,6-dianhydro-d-mannitol 119 [181][182][183][184] yielded two equivalents of an ethynylated aldehyde. Treatment of 119 with the hexa-1,5-diyne 121 derived from diethyl l-tartrate (reduction and Corey-Fuchs reaction) gave the C 2 -symmetric cyclododeca-1,5-diyne 122, albeit in only 30 % yield [184].…”

“…Treatment of 119 with the hexa-1,5-diyne 121 derived from diethyl l-tartrate (reduction and Corey-Fuchs reaction) gave the C 2 -symmetric cyclododeca-1,5-diyne 122, albeit in only 30 % yield [184].…”

Oxidation of Alcohols to Aldehydes and Ketones

“…Ref.158a Treatment of the tertiary allylic alcohol with PDC results in transposition of the intermediate chromate ester, producing a transposed enal.Nevertheless, normally it is possible to selectively oxidize primary and secondary alcohols with PDC without aVecting tertiary allylic alcohols 159. Ref 160. An uneventful oxidation of a secondary alcohol occurs with no oxidative transposition to enone of the tertiary allylic alcohol.Sometimes, tertiary allylic alcohols interfere with the oxidation of primary and secondary alcohols with PDC, causing low-yielding transformations into the desired aldehydes and ketones.…”