No abstract

Homoallylic carbamates bearing an α,β-unsaturated ester or an allylic carbonate were generated respectively utilizing novel chiral silanes through Lewis acid promoted asymmetric aminocrotylation. Those bifunctional building blocks could further undergo Michael addition or cyclization to selectively form functionalized lactams, azetidines, and tetrahydropyrimidinones.

Ia search of M V~ p@ derivatives with biosctivity, a se-diverse biological activities. Many pyrazole compounds exhibit excellent bioactivity. Some of them have been were used as herbicides, ' insecticides ,2 fiqcides3 and acariterial* stnrtuRs of mnpamQ prrparrd were ~i d e s .~ In previous works, we have synthesized many f I n m d b y ' H N M R , I R , M S d d~t d a d~.~pyrazole derivatives with bioactivity . nary biomsnp Indicated that SOIm campamdprcmsici-Sulfamide derivatives m a kind of important herbidal adivity against w h d nrst, pharmr uspfm& and d v i d activity ageimt w. cide. If sulfonyls are introduced into pyrazole ring, sul-3-methyl-fH-Wrazole-qcaboxyiic * dithioecccab fonyls may enhance biological activities. For example, 1triazolesulfonyl-1 H-pyrezoles poesess excellent herbicidal a~tivity.~ AS part of ow ongoing p m p m aimed at SeaTChing for apchemicals, our interests in the pyrazole compounds containing sulfonyl led us to synthesize a novel series of 1-sdfonyl (methyl, formy1)-3-methyl-5b q f i o ( h q l t h i o , bflybUlfonyl)-1 ~-~ ~& q l i c atem.scheme2 7 H 8 Results and discussionThe a-oxoketene dithioacetals 1 reacted with bemyl amine to give a-oxoketene N , S-aced 2, which was cyclized in ethanol with hydrazine hydrate (80% ) to give 3-methyl-5-bemylamino-1 H-pyrazole4carboxylic ester 3. Compound 3 was methylated, sulfonylated and formylated with iodomethane, sulfonyl chloride and formyl chloride to yield 1-methylpyrazole 5, 1-sulfonylpyrazoles 4 and 1 -formylpyrazoles 6, respectively.

Three‐component aminocrotylation reaction of the novel silanes (I) and (XIII) leads to homoallylic carbamates bearing an unsaturated ester or allylic carbonate in good syn‐selectivity.

A Detailed Investigation into the Oxidation Mechanism of Hantzsch 1,4-Dihydropyridines by Ethyl α-Cyanocinnamates and Benzylidenemalononitriles. -Correlation analyses on kinetics, kinetic isotope effects, and activation parameters confirm the one-step hydride transfer mechanism, proposed for the oxidation of Hantzsch ester (I) by α,β-unsaturated esters or nitriles (IIa) or (IIb) to form Hantzsch pyridine (III) in quantitative yield. -